@article{EL2013,
  author = {Gregor Engels AND Markus Luckey},
  title = {Editorial},
  journal = {Computer Science - Research and Development},
  year = {2013},
  volume = {28},
  number = {1},
  pages = {1--2},
  month = {Januar},
  note = {Organ der Fachbereiche Softwaretechnik, Datenbanken und Informationssysteme der Gesellschaft f{\"u}r Informatik e.V. (GI)}
}

@article{DEK-2012,
  author = {Uwe Dumslaff AND Gregor Engels AND Marion Kremer},
  title = {IT ist nicht gleich IT: Ein Pl{\"a}doyer f{\"u}r eine situationsbezogene Softwareentwicklung},
  journal = {OBJEKTspektrum},
  year = {2012},
  number = {Nr. 5},
  pages = {52 - 57},
  month = {September},
  note = {Fachzeitschrift TroisdorfCapgemini}
}

@article{luckey_jvlc12,
  author = {Markus Luckey AND Martin Erwig AND Gregor Engels},
  title = {Systematic Evolution of Model-Based Spreadsheet Applications},
  journal = {Journal of Visual Languages and Computing},
  year = {2012},
  volume = {23},
  number = {5},
  pages = {267-286},
  month = {Oct}
}

@article{EW2012,
  author = {Gregor Engels AND Jon Whittle},
  title = {Ten years of software and systems modeling},
  journal = {Software and Systems Modeling},
  year = {2012},
  volume = {11},
  number = {4},
  pages = {467--470},
  month = {October},
  note = {Softw Syst. Model (2012) 11:467-470}
}

@article{GerthSoSym11,
  author = {Christian Gerth AND Jochen K{\"u}ster AND Markus Luckey AND Gregor Engels},
  title = {Detection and Resolution of Conflicting Change Operations in Version Management of Process Models},
  journal = {Software and Systems Modeling},
  year = {2011},
  pages = {1-19},
  month = {December},
  abstract = {Version management of process models requires that different versions of process models are integrated by applying change operations. Conflict detection between individually applied change operations and conflict resolution support are integral parts of version management. For conflict detection it is utterly important to compute a precise set of conflicts, since the minimization of the number of detected conflicts also reduces the overhead for merging different process model versions. As not every syntactic conflict leads to a conflict when taking into account model semantics, a computation of conflicts solely on the syntax leads to an unnecessary high number of conflicts. Moreover, even the set of precisely computed conflicts can be extensive and their resolution means a significant workload for a user. As a consequence, adequate support is required that guides a user through the resolution process and suggests possible resolution strategies for individual conflicts. In this paper, we introduce the notion of syntactic and semantic conflicts for change operations of process models. We provide a method how to efficiently compute conflicts precisely, using a term formalization of process models and consider the subsequent resolution of the detected conflicts based on different strategies. Using this approach, we can significantly reduce the number of overall conflicts and reduce the amount of work for the user when resolving conflicts.}
}

@article{gfse11,
  author = {Baris G{\"u}ldali AND Holger Funke AND Stefan Sauer AND Gregor Engels},
  title = {TORC: test plan optimization by requirements clustering},
  journal = {Software Quality Journal},
  year = {2011},
  pages = {1-29},
  note = {10.1007/s11219-011-9149-4},
  abstract = {Acceptance testing is a time-consuming task for complex software systems that have to fulfill a large number of requirements. To reduce this effort, we have developed a widely automated method for deriving test plans from requirements that are expressed in natural language. It consists of three stages: annotation, clustering, and test plan specification. The general idea is to exploit redundancies and implicit relationships in requirements specifications. Multi-viewpoint techniques based on RM-ODP (Reference Model for Open Distributed Processing) are employed for specifying the requirements. We then use linguistic analysis techniques, requirements clustering algorithms, and pattern-based requirements collection to reduce the total effort of testing against the requirements specification. In particular, we use linguistic analysis for extracting and annotating the actor, process and object of a requirements statement. During clustering, a similarity function is computed as a measure for the overlap of requirements. In the test plan specification stage, our approach provides capabilities for semi-automatically deriving test plans and acceptance criteria from the clustered informal textual requirements. Two patterns are applied to compute a suitable order of test activities. The generated test plans consist of a sequence of test steps and asserts that are executed or checked in the given order. We also present the supporting prototype tool TORC, which is available open source. For the evaluation of the approach, we have conducted a case study in the field of acceptance testing of a national electronic identification system. In summary, we report on lessons learned how linguistic analysis and clustering techniques can help testers in understanding the relations between requirements and for improving test planning.}
}

@article{SE2010,
  author = {Christian Soltenborn AND Gregor Engels},
  title = {Using Rule Overriding to Improve Reusability and Understandability of Dynamic Meta Modeling Specifications},
  journal = {Journal of Visual Languages and Computing},
  year = {2011},
  volume = {22},
  number = {3},
  pages = {233--250},
  abstract = {Dynamic Meta Modeling (DMM) is a visual semantics specification technique targeted at languages based on a metamodel. A DMM specification consists of a runtime metamodel and operational rules which describe how instances of the runtime metamodel change over time. A known deficiency of the DMM approach is that it does not support the refinement of a DMM specification, e.g., in the case of defining the semantics for a refined and extended domain-specific language (DSL). Up to now, DMM specifications could only be reused by adding or removing DMM rules.In this paper, we enhance DMM such that DMM rules can override other DMM rules, similar to a method being overridden in a subclass, and we show how rule overriding can be realized with the graph transformation tool GROOVE. We argue that rule overriding does not only have positive impact on reusability, but also improves the intuitive understandability of DMM semantics specifications.}
}

@article{GEArtic09,
  author = {Gregor Engels},
  title = {Guest Editorial to the Special Section on MODELS 2007},
  journal = {Software \& Systems Modeling},
  year = {2010},
  volume = {9},
  number = {1},
  pages = {5--6},
  month = {Januar}
}

@article{EGGRR09,
  author = {Gregor Engels AND Michael Goedicke AND Ursula Goltz AND Andreas Rausch AND Ralf H. Reussner},
  title = {Design for Future -- Legacy-Probleme von morgen vermeidbar?},
  journal = {Informatik-Spektrum},
  year = {2009},
  volume = {32},
  number = {5},
  pages = {393--397},
  month = {Oktober}
}

@article{egs08,
  author = {Baris G{\"u}ldali AND Stefan Sauer AND Gregor Engels},
  title = {Formalisierung der funktionalen Anforderungen mit visuellen Kontrakten und deren Einsatz f{\"u}r modellbasiertes Testen},
  journal = {Softwaretechnik-Trends},
  year = {2008},
  volume = {28},
  number = {3},
  pages = {12-16},
  month = {August},
  abstract = {Wir haben in diesem Beitrag einen Ansatz zurFormalisierung der UML-Anwendungsfallsbeschreibungenvorgestellt, um Anwendungsf{\"a}lleeffektiv f{\"u}r Testzwecke einsetzen zu k{\"o}nnen.Dabei werden die textuellen Beschreibungen derVor- und Nachbedingungen mit visuellen Kontraktenformalisiert. Die visuellen Kontrakte beschreibendie {\"A}nderungen bez{\"u}glich der fachlichenDaten nach der Ausf{\"u}hrung des Anwendungsfalls.Mit visuellen Kontrakten k{\"o}nnenw{\"a}hrend der Testfallspezifikation Testeingabengeneriert und w{\"a}hrend der Testausf{\"u}hrung Testausgaben{\"u}berpr{\"u}ft werden. F{\"u}r visuelle Kontraktewurden Werkzeuge entwickelt, die dieEinbindung der visuellen Kontrakte in den Entwicklungs-und Testprozess erm{\"o}glichen.}
}

@article{EngVo08,
  author = {Gregor Engels AND Markus Vo{\ss}},
  title = {Quasar Enterprise},
  journal = {Informatik-Spektrum},
  year = {2008},
  volume = {31},
  number = {6},
  pages = {548--555},
  abstract = {Die Gestaltung und Weiterentwicklung gro{\ss}er Anwendungslandschaften gilt heutzutage als eine der gr{\"o}{\ss}ten Herausforderungen in der Softwaretechnik. Als L{\"o}sungsansatz wurde in den letzten Jahren vielfach das Paradigma einer serviceorientierten Architektur (SOA) diskutiert und insbesondere durch herstellerspezifische Technologien unterst{\"u}tzt. Dieser Beitrag widmet sich einer h{\"a}ufig vernachl{\"a}ssigten methodischen Herangehensweise und stellt mit Quasar Enterprise einen strukturierten und in der Praxis erprobten L{\"o}sungsansatz vor. Insbesondere werden konkrete Verfahrensbausteine f{\"u}r eine durchg{\"a}ngige Methode vorgestellt, die einem Architekten helfen, eine auf das zu unterst{\"u}tzende Gesch{\"a}ft ausgerichtete Anwendungslandschaft zu entwickeln und zu warten. Wesentliche Charakteristika von Quasar Enterprise sind der konsequente Einsatz einer serviceorientierten Herangehensweise, die Verwendung eines Architektur-Frameworks als Strukturierungsgrundlage und die Aufbereitung der Methode in Form von 20 Verfahrensbausteinen.}
}

@article{ESS2008,
  author = {Gregor Engels AND Stefan Sauer AND Christian Soltenborn},
  title = {Unternehmensweit verstehen -- unternehmensweit entwickeln: Von der Modellierungssprache zur Softwareentwicklungsmethode},
  journal = {Informatik-Spektrum},
  year = {2008},
  volume = {31},
  number = {5},
  pages = {451--459},
  month = {October},
  abstract = {Sollen wir UML 1.4, UML 2.0 oder eine ganz andere Modellierungssprache f{\"u}r unsere Softwareentwicklung einsetzen? Der folgende Beitrag zeigt, dass bei der Festlegung einer unternehmensweiten Entwicklungsmethode nicht die Frage nach der Modellierungssprache im Vordergrund stehen sollte. Viel entscheidender f{\"u}r den Erfolg von Softwareentwicklungsprojekten in einem Unternehmen ist ein einheitliches Verst{\"a}ndnis der Entwicklungskonzepte und -artefakte sowie ihrer Beziehungen untereinander. Eine Einigung {\"u}ber ein unternehmensweites Dom{\"a}nenmodell der Softwareentwicklungskonzepte sollte deshalb vor der Auswahl von Modellierungssprachen, eines konkreten Vorgehensmodells und geeigneter Werkzeuge erfolgen.}
}

@article{Bals2007,
  author = {Jan-Christopher Bals AND Fabian Christ AND Gregor Engels AND Stefan Sauer},
  title = {Software-Qualit{\"a}t - {\"u}berall! - Excel-lente Software},
  journal = {Forschungsforum Paderborn},
  year = {2007},
  volume = {10},
  pages = {56--60},
  month = {January}
}

@article{Doberkat2005,
  author = {Ernst-Erich Doberkat AND Gregor Engels AND Jan Hendrik Hausmann AND Marc Lohmann AND J{\"o}rg Pleumann AND Jens Schr{\"o}der},
  title = {Software Engineering and eLearning: The MuSofT Project},
  journal = {e-learning and education (eleed) Journal},
  year = {2005},
  volume = {2},
  month = {Dezember},
  abstract = {eLearning supports the education in certain disciplines. Here, we report about novel eLearning concepts, techniques, and tools to support education in Software Engineering, a subdiscipline of computer science. We call this "Software Engineering eLearning". On the other side, software support is a substantial prerequisite for eLearning in any discipline. Thus, Software Engineering techniques have to be applied to develop and maintain those software systems. We call this "eLearning Software Engineering". Both aspects have been investigated in a large joint, BMBF-funded research project, termed MuSofT (Multimedia in Software Engineering). The main results are summarized in this paper.}
}

@article{Engels2003a,
  author = {Gregor Engels AND Jan Hendrik Hausmann AND Marc Lohmann},
  title = {eLearning-Plattformen f{\"u}r die Hochschule: Bedarfsgerechte Bestimmung der Anforderungen},
  journal = {ForschungsForum Paderborn},
  year = {2003},
  volume = {6},
  pages = {44--47},
  month = {January},
  abstract = {Der Einfluss neuer Technologien auf die Art wie wir Lehren und Lernen wird seit einigen Jahren unter dem Begriff eLearning diskutiert. Auch an den Hochschulen gibt es Bemhungen, eLearning-Konzepte zu etablieren. Dabei versprechen so genannte eLearning-Plattformen ein integriertes und reibungsloses Zusammenarbeiten aller Beteiligten am eLearning zu ermglichen. Der Einsatz einer so zentralen Software in einem System wie der Hochschule ist ein komplexes Problem, fr dessen Bewltigung die Softwaretechnik, ein Fachgebiet der Informatik, Methoden und Sprachen bereitstellt. Zentrale Idee dabei ist es, von existierenden Strukturen und den Bedrfnissen der Anwender auszugehen. In diesem Beitrag wird beschrieben, wie die Analyse von Hochschulstrukturen und Prozessen der Planung des Einsatzes von eLearning-Plattformen dient.}
}

@article{EngelsKG2002c,
  author = {Gregor Engels AND Jochen K{\"u}ster AND Luuk Groenewegen},
  title = {Consistent Interaction of Software Components},
  journal = {Transactions of the SDPS: Journal of Integrated Design \& Process Science},
  year = {2002},
  volume = {6},
  number = {4},
  pages = {2--22},
  month = {December},
  abstract = {Constructing complex software systems by integrating different software components isa promising and challenging approach. With the functionality of software components given by models it is possible to ensure consistency of such models before implementation in order to successfully build the system. Models consisting of different submodels, the absence of an overall formal semantics and the numerous possibilities of employing models requires the development of techniques ensuring the consistency. In this paper, we discuss the issue of consistency of models made up of different submodels proposing a concept for the management of consistency. Consistency management relies on a consistency concept and a process for ensuring consistency of models. We introduce a consistency concept for software components modeled in the Unified Modeling Language (UML) and devise suitable consistency checks. On this basis, we propose a process how to locate and resolve inconsistencies, thus ensuring the consistency of models and by that the consistency of componentbased systems derived from those models.}
}

@article{Doberkat2002,
  author = {Ernst-Erich Doberkat AND Gregor Engels},
  title = {MuSofT - Multimedia in der Softwaretechnik},
  journal = {Informatik Forschung und Entwicklung},
  year = {2002},
  volume = {1},
  number = {17},
  pages = {41--44},
  month = {Februar},
  abstract = {Im BMBF-Verbundprojekt MuSofT werden multimediale Lehrmaterialienf{\"u}r die Lehre der Softwaretechnik entwickelt. Neben den inhaltliche Aspekten sind dieDistribution und die Lizenzierung der erstellten Lehrmaterialien wichtige Themakomplexe,um die Nachhaltigkeit des Projektes zu erh{\"o}hen. In diesem Papier stellen wirdie in MuSofT gew{\"a}hlten L{\"o}sungen einer Open-Content-Lizenz sowie eines Portalszur Distribution der entwickelten Materialien vor.}
}

@article{Engels2001,
  author = {Gregor Engels AND Jens Gaulke AND Stefan Sauer},
  title = {Modelle f{\"u}r automobile Software - Objektorientierte Modellierung von eingebetteten, interaktiven Softwaresystemen im Automobil},
  journal = {Forschungsforum Paderborn},
  year = {2001},
  volume = {4},
  pages = {24--29},
  month = {January},
  abstract = {Wie in allen technischen Ger{\"a}ten werden auch im Automobil immer mehr Funktionen durch Softwaresysteme realisiert bzw. gesteuert. Bei einer Entwicklung derartiger Softwaresysteme wird im Rahmen eines ingenieurm{\"a}{\ss}igen Entwicklungsprozesses zun{\"a}chst ein Modell erstellt. Hierzu muss eine Modellierungssprache zur Verf{\"u}gung stehen, die den Modellierer ad{\"a}quat bei der Erstellung des Modells unterst{\"u}tzt und ein einheitliches Verst{\"a}ndnis des Modells erm{\"o}glicht. }
}

@article{HE00,
  author = {Gregor Engels AND Reiko Heckel},
  title = {Graph Transformation and Visual Modeling Techniques},
  journal = {Bulletin of the EATCS},
  year = {2000},
  number = {71},
  pages = {186--202},
  month = {June},
  abstract = {In order to provide semantic support for visual modeling techniques, new techniques have to be developed which help us to narrow the conceptual gap between graph-based visual modeling techniques like the UML and established methodologies of programming language semantics almost exclusively based on trees and terms. Concepts and results from the area of graph transformation can be used both as a basis for high-level rule-based visual languages, and as semantic domain for visual modeling techniques focusing on the structural and behavioral aspects of today's software systems. Moreover, graph transformation can provide the necessary technology in order to develop the graph-based counterparts of the denotational, operational, or algebraic semantics paradigms in the field of programming languages.In this paper, we substantiate these claims by examples of the use of graph transformation as visual modeling notion, semantic domain, and for the semantics of diagram languages.}
}

@article{Depke1999,
  author = {Ralph Depke AND Gregor Engels AND Katharina Mehner AND Stefan Sauer AND Annika Wagner},
  title = {Ein Vorgehensmodell f{\"u}r die Multimedia-Entwicklung mit Autorensystemen},
  journal = {Informatik Forschung und Entwicklung},
  year = {1999},
  volume = {14},
  number = {2},
  pages = {83--94},
  month = {June},
  abstract = {Multimedia-Anwendungen sind interaktive Softwaresysteme und verlangen als solche, mit softwaretechnischen Methoden erstellt zu werden. Sie werden heutzutage in der Regel mit Hilfe von Autorensystemen entwickelt, die eine Ad-hoc-Entwicklung auf Implementierungsniveau unterst{\"u}tzen. Hierdurch und wegen des Fehlens etablierter Vorgehensmodelle f{\"u}r die Multimedia-Softwareentwicklung reduziert sich der Multimedia-Entwicklungsproze{\ss} auf die Implementierungsphase. Dies f{\"u}hrt zu den in der Softwaretechnik bekannten Problemen wie mangelnder Konzeption und fehlender Dokumentation. Wir stellen in diesem Beitrag ein Vorgehensmodell f{\"u}r die Entwicklung von Multimedia-Anwendungen vor, in dessen Mittelpunkt eine Analyse- und Entwurfsphase im Hinblick auf eine Implementierung der Multimedia-Anwendung mit einem Autorensystem stehen. Ausgehend von einem frameworkbasierten Analysemodell der Anwendung und einem Modell der Realisierungsm{\"o}glichkeiten mit einem konkreten Autorensystem wird systematisch ein Implementierungsmodell auf Instanzebene abgeleitet, das als Eingabe f{\"u}r das Autorensystem verwendet wird. Das postulierte Vorgehensmodell wird exemplarisch f{\"u}r das Autorensystem Director am Beispiel der Dom{\"a}ne multimedialer Lehr-/Lernanwendungen erl{\"a}utert.}
}

@article{Andries1999,
  author = {Marc Andries AND Gregor Engels AND Annegret Habel AND Berthold Hoffmann AND Hans-J{\"o}rg Kreowski AND Sabine Kuske AND Detlef Plump AND Andy Sch{\"u}rr AND Gabriele Taentzer},
  title = {Graph Transformation for Specification and Programming},
  journal = {Science of Computer Programming},
  year = {1999},
  volume = {34},
  number = {1},
  pages = {1--54},
  month = {April },
  abstract = {The framework of graph transformation combines the potentials and advantages of both, graphs and rules, to a single computational paradigm. In this paper we present some recent developments in applying graph transformations as a rule-based framework for the specification and development of systems, languages, and tools. After reviewing the basic features of graph transformation, we discuss a selection of applications, including the evaluation of functional expressions, the specification of an interactive graphical tool, an example specification of abstract data types, and the definition of a visual database query language. The case studies indicate the need for suitable structuring principles which are independent of a particular graph transformation approach. To this end, we present the concept of a transformation unit, which allows systematic and structured specifications and programming based on graph transformation.}
}

@article{EHTE97b,
  author = {Gregor Engels AND Reiko Heckel AND Gabriele Taentzer AND Hartmut Ehrig},
  title = {A Combined Reference Model- and View-Based Approach to System Specification},
  journal = {Int. Journal of Software and Knowledge Engeneering},
  year = {1997},
  volume = {7},
  number = {4},
  pages = {457--477},
  month = {December},
  abstract = {The idea of a combined reference model- and view-based specification approach has been proposed recently in the software engineering community. In this paper we present a specification technique based on graph transformations which supports such a development approach. The use of graphs and graph transformations allows to satisfy the general requirements of an intuitive understanding and the integration of static and dynamic aspects on a well-defined and sound semantical base. On this background, formal notions of view and view relation are developed and the behaviour of views is described by a loose semantics. View relations are shown to preserve the behaviour of views. Moreover, we define a construction for the automatic integration of views which assumes that the dependencies between different views are described by a reference model. The views and the reference model are kept consistent manually, which is the task of a model manager. In case of more than two views more general scenarios are developed and discussed. We are able to show that the automatic view integration is compatible with the loose semantics, i.e., the behaviour of the system model is exactly the integration of the behaviours of the views. All concepts and results are illustrated at the well-known example of a banking system.}
}

@article{Engels97a,
  author = {Gregor Engels AND Hans J{\"u}rgen Schneider},
  title = {Guest Editors' Introduction},
  journal = {International Journal on Software Engineering and Knowledge Engineering (IJSEKE)},
  year = {1997},
  volume = {7},
  number = {4},
  pages = {397--400},
  month = {December },
  note = {},
  abstract = {Guest Editors Introduction}
}

@article{Andries1996,
  author = {Marc Andries AND Gregor Engels},
  title = {A Hybrid Query Language for the Extended Entity Relationship Model},
  journal = {Journal of Visual Languages and Computing},
  year = {1996},
  volume = {7},
  number = {3},
  pages = {321--352},
  month = {September},
  abstract = {We present the hybrid query language HQL/EER for an Extended Entity-Relationship model. As its main characteristic, this language allows a user to usebothgraphical and textual elements in the formulation of one and the same query. We demonstrate the look-and-feel of this query language by means of examples, and show how syntax and semantics of this language are formally defined using programmed graph rewriting systems. Although we present the language in the context of the EER model, the concept of hybrid languages is applicable in the context of other database models as well. We illustrate this claim by discussing a prototype implementation of a Hybrid Query Tool based on an object-oriented approach, namely the Object Modeling Technique (OMT).}
}

@article{Loehr-Richter1994,
  author = {Perdita L{\"o}hr-Richter AND Gregor Engels},
  title = {Visuelles Spezifizieren von komplexen Aktionen auf Datenbankstrukturen},
  journal = {GI-Datenbank Rundbrief},
  year = {1994},
  volume = {13},
  pages = {33--35},
  month = {March}
}

@article{EngelsLNSS1992,
  author = {Gregor Engels AND Claus Lewerentz AND Manfred Nagl AND Wilhelm Sch{\"a}fer AND Andy Sch{\"u}rr},
  title = {Building Integrated Software Development Environments, Part I: Tool Specification},
  journal = {ACM Transactions on Software Engineering and Methodology (TOSEM)},
  year = {1992},
  volume = {1},
  number = {2},
  pages = {135--167},
  month = {April},
  abstract = {The conceptual modeling approach of the IPSEN (Integrated Project Support Environment) project for building highly integrated environments is based on using attributed graphs to model and implement arbitrary object structures, in particular all kinds of software documents and their relationships. A language based on graph grammars, called PROGRESS (Programmed Graph REwriting SyStems), and a suitable method for the application of this language, called graph grammar engineering, have been developed over the last ten years. This language and method are being extensively used for specifying the complex graph structures of internal document representations as well as for specifying the functionality of all tools (editors, browsers, analyzers, debuggers) working on these internal representations. This paper explains the language and the method for applying the language based on a pragmatic nontrivial example of a software production process and its corresponding documents. In particular, it is shown why and how a graph grammar-based strongly typed language is perfectly suitable to formally specify highly integrated software tools. In addition, it is shown that the implementation of these tools (i.e., an environment composed of these tools) is systematically being derived from the formal specifications.}
}

@article{Engels1992a,
  author = {Gregor Engels AND Martin Gogolla AND Uwe Hohenstein AND Klaus H{\"u}lsmann AND Perdita L{\"o}hr-Richter AND Gunter Saake AND Hans-Dietrich Ehrich},
  title = {Conceptual Modelling of Database Applications Using an Extended ER Model},
  journal = {Data \& Knowledge Engineering},
  year = {1992},
  volume = {9},
  number = {2},
  pages = {157--204},
  month = {December},
  abstract = {In this paper, we motivate and present a data model for conceptual design of structural and behavioural aspects of databases. We follow an object centered design paradigm in the spirit of semantic data models. The specification of structural aspects is divided into modelling of object structures and modelling of data types used for describing object properties. The specification of object structures is based on an Extended Entity--Relationship (EER) model. The specification of behavioural aspects is divided into the modelling of admissible database state evolutions by means of temporal integrity constraints and the formulation of database (trans)actions. The central link for integrating these design components is a descriptive logic--based query language for the EER model. The logic part of this language is the basis for static constraints and descriptive action specifications by means of pre- and postconditions. A temporal extension of this logic is the specification language for temporal integrity constraints. We emphasize that the various aspects of a database application are specified using several appropriate, but yet compatible formalisms, which are integrated by a unifying common semantic.}
}

@article{Hohenstein1992,
  author = {Uwe Hohenstein AND Gregor Engels},
  title = {SQL/EER - Syntax and Semantics of an Entity-Relationship-Based Query Language},
  journal = {Information Systems},
  year = {1992},
  volume = {17},
  number = {3},
  pages = {209--242},
  abstract = {This paper presents the high-level query language SQL/EER for an extended Entity-Relationship model (EER model). SQL/EER directly supports all the concepts of the EER model and takes into account well-known features that are integral part of contemporary query languages, e.g. arithmetic and aggregate functions. In contrast to usual descriptions of query languages, we give SQL/EER a complete formal specification of syntax and sematics. This syntax is defined by using an attribute grammar which fixes the context-free structure and the context-sensitive rules. The operational semantics is defined by formally translating SQL/EER queries into queries of an existing, semantically well-defined calculus. The attribute grammar is extended to cover this translation, too.The query language SQL/EER is used in a database design environment. In this context, the formal specification of its syntax and the semantics has been used to implement a syntax-directed editor and a query interpreter for SQL/EER.}
}

@article{Engels1983,
  author = {Gregor Engels AND Udo Pletat AND Hans-Dietrich Ehrich},
  title = {An Operational Semantics for Specifications of Abstract Data Types with Error Handling},
  journal = {Acta Informatica},
  year = {1983},
  volume = {9},
  number = {3},
  pages = {235--254},
  abstract = {A new approach to an operational treatment of errors and exceptions in specifications of abstract data types is presented. Considering a specification as a term rewriting system, we define an operational semantics and give conditions that are sufficient for its well-definedness (Church-Rosser property). Also, we give conditions that are sufficient for the termination of reduction strategies, respecting the specified error and exception handling.}
}

@article{Engels1983a,
  author = {Gregor Engels AND Rupert Gall AND Manfred Nagl AND Wilhelm Sch{\"a}fer},
  title = {Software Specification Using Graph Grammars},
  journal = {Computing},
  year = {1983},
  volume = {31},
  number = {4},
  pages = {317--346},
  month = {December},
  abstract = {The following paper,demonstrates that programmed sequential graph grammars can be used in a systematic proceeding to specify tbe changes of high level intermediate data structures arising in a programming support environment, in which all tools work in an incremental and syntax-driven mode. In this paper we lay stress upon the way to get the specification rather than on the result of this process. Therefore, we give here some approach to "specification engineering" using graph grammars. This approach is influenced by the syntactical definition of the underlying language for Programming in the Small, the module concept etc. to be supported on one side but also by the idea of the user interface.}
}

@book{KEHNPSW-2012,
  author = {Marion Kremer AND Gregor Engels AND Alexander Hofmann AND J{\"o}rg Hohwiller AND Oliver E. Nandico AND Thomas N{\"o}tzold AND Karl Prott AND Diethelm Schlegel AND Andreas Seidl AND Thomas Wolf},
  title = {Quasar 3.0 - A Situational Approach to Software Engineering},
  publisher = {Capgemini CSD Research, Offenbach 2012},
  year = {2012},
  month = {Juni}
}

@book{Engels2008,
  author = {Gregor Engels AND Andreas Hess AND Bernhard Humm AND Oliver Juwig AND Marc Lohmann AND Jan-Peter Richter AND Markus Vo{\ss} AND Johannes Willkomm},
  title = {Quasar Enterprise: Anwendungslandschaften serviceorientiert gestalten},
  publisher = {dpunkt-Verlag},
  year = {2008},
  address = {M{\"u}nchen},
  month = {M{\"a}rz},
  abstract = {IT-Anwendungslandschaften in Unternehmen sind komplexe {\"u}ber Jahre gewachsene Gebilde. Sie architektonisch zu gestalten und nachhaltig zu entwickeln braucht eine eigene Technologie jenseits der klassischen Softwaretechnik. Der Ansatz serviceorientierter Architekturen (SOA) ist ein wichtiges Instrument, reicht aber alleine nicht aus.In Quasar Enterprise haben Experten des Softwareunternehmens sd\&m eine durchg{\"a}ngige Architekturmethodik f{\"u}r die serviceorientierte Gestaltung von Anwendungslandschaften zusammengetragen, die Erfahrungen aus Dutzenden von Beratungs-, Integrations- und gro{\ss}en Softwareprojekten widerspiegelt. Das Besondere an Quasar Enterprise ist die Sammlung sehr konkreter Methoden, Regeln, Referenzarchitekturen und Muster f{\"u}r die Gestaltung - ausgehend von der Architektur des Gesch{\"a}fts, {\"u}ber die logische Strukturierung der IT in Services und Dom{\"a}nen, bis hin zu physischen Komponenten und Schnittstellen inkl. deren Kopplung {\"u}ber technische Integrationsplattformen.Teil I beschreibt ein fiktives, aber realistisches Projekt aus der Sicht eines IT-Architekten. Der Leser schaut ihm bei seiner Arbeit {\"u}ber die Schulter und erlangt dabei ein intuitives Verst{\"a}ndnis der Artefakte und Verfahrensbausteine von Quasar Enterprise. Das Vorgehen im Projekt erlebt er dabei beispielhaft.Teil II vertieft das Erlernte systematisch. Die Grundlagen f{\"u}r Anwendungslandschaften und SOA werden eingef{\"u}hrt und dann Schritt f{\"u}r Schritt Begriffe, Zusammenh{\"a}nge und Vorgehensbausteine erl{\"a}utert. Die Beziehungen zwischen Architekturentscheidungen und Qualit{\"a}tszielen werden transparent gemacht und Verweise auf weiterf{\"u}hrende Literatur gegeben. Das Buch richtet sich an alle, die etwas {\"u}ber Anwendungslandschaften und SOA in der Praxis wissen wollen. Prim{\"a}re Zielgruppe sind IT-Architekten, erfahrene Softwareingenieure und Berater. }
}

@book{Engels1989,
  author = {Gregor Engels AND Wilhelm Sch{\"a}fer},
  title = {Programmentwicklungsumgebungen: Konzepte und Realisierung},
  publisher = {Teubner},
  year = {1989},
  address = {Stuttgart}
}

@inproceedings{PDBSE-2013,
  author = {Marie Christin Platenius AND Markus von Detten AND Steffen Becker AND Wilhelm Sch{\"a}fer AND Gregor Engels},
  title = {A Survey of Fuzzy Service Matching Approaches in the Context of On-The-Fly Computing},
  booktitle = {In: Proceedings of the 16th International ACM Sigsoft Symposium on Component-Based Software Engineering},
  year = {2013},
  organization = {ACM},
  month = {Juni},
  note = {17. - 21. Jun. 2013, ACM}
}

@inproceedings{wachsmuth:2013a,
  author = {Henning Wachsmuth AND Mirko Rose AND Gregor Engels},
  title = {Automatic Pipeline Construction for Real-Time Annotation},
  booktitle = {Proceedings of the 14th International Conference on Intelligent Text Processing and Computational Linguistics},
  year = {2013},
  editor = {Alexander Gelbukh},
  pages = {38-49},
  publisher = {Springer},
  address = {Samos, Greece},
  month = {March},
  abstract = {Many annotation tasks in computational linguistics are tackled with manually constructed pipelines of algorithms. In real-time tasks where information needs are stated and addressed ad-hoc, however, manual construction is infeasible. This paper presents an artificial intelligence approach to automatically construct annotation pipelines for given information needs and quality prioritizations. Based on an abstract ontological model, we use partial order planning to select a pipeline's algorithms and informed search to obtain an efficient pipeline schedule. We realized the approach as an expert system on top of Apache UIMA, which offers evidence that pipelines can be constructed ad-hoc in near-zero time.},
  series = {LNCS},
  volume = {7816}
}

@inproceedings{bruBecEng2013-1,
  author = {Frank Br{\"u}seke AND Steffen Becker AND Gregor Engels},
  title = {Decision Support via Automated Metric Comparison for the Palladio-based Performance Blame Analysis},
  booktitle = {Proceedings of the 4th ACM/SPEC International Conference on Performance Engineering (ICPE 2013), Prague (Czech Republic)},
  year = {2013},
  publisher = {to be published},
  note = {to be published},
  abstract = {When developing component-based systems, we incorporate third-party black-box components. For each component, performance contracts have been specified by their developers. If errors occur within the system built from these components, it is very important to find out whether components violate their performance contracts or whether the composition itself is faulty. This task is called performance blame analysis. In our previous work we presented a performance blame analysis approach that blames components based on a comparison of response time values from testing to values derived from the performance contract. In that approach, the system architect needs to manually assess if the test data series shows faster or slower response times than the data derived from the contract. This is laborious as the system architect has to do this for each component operation. In this paper we present an automated comparison of each pair of data series as decision support. In contrast to our work, other approaches do not achieve fully automated decision support, because they do not incorporate sophisticated contracts. We exemplify our performance blame analysis including the automated decision support using the "Common Component Modeling Example" (CoCoME) benchmark.}
}

@inproceedings{EDOC13_Nagel,
  author = {Benjamin Nagel AND Christian Gerth AND Jennifer Post AND Gregor Engels},
  title = {Ensuring Consistency Among Business Goals and Business Process Models},
  booktitle = {Proceedings of the 17th IEEE International EDOC Conference (EDOC'13) (accepted for publication)},
  year = {2013},
  publisher = {IEEE Computer Society},
  abstract = {The paradigm of service-oriented architectureshas emerged as an architectural style for designing enterprise applications. Requirements engineering for such applications comprises the specification of business goal models representingstakeholder objectives and the operationalization to business process models that specify the required composition of services. Inconsistencies between business goals and derived business processes can lead to service compositions that are notin line with the actual stakeholder objectives. For preserving consistency it is required to consider logical and temporal dependencies among goals (e.g. the order in which they need to be achieved) in the derivation of business processes. In previous work, we provided a technique for the elicitation andspecification of dependencies between business goals. Extending this approach, we aim at validating the consistency betweenbusiness goal models and business process models regarding these dependencies. In this paper, we present a pattern-based approach for the automated generation of verifiable business process quality constraints from business goal models. We describe how these constraints can be used to check the consistency between business goals and business processes and demonstrate the applicability of our approach in a case studyby using the implemented tool support.}
}

@inproceedings{acml_seams13,
  author = {Markus Luckey AND Gregor Engels},
  title = {High-­Quality Specification of Self-­Adaptive Software Systems},
  booktitle = {Proceeding of the 8th international symposium on Software engineering for adaptive and self-managing systems},
  year = {2013},
  publisher = {ACM (to appear)},
  address = {New York, NY, USA},
  month = {May},
  series = {SEAMS '13}
}

@inproceedings{SGENH2013,
  author = {Claudia Schumacher AND Baris G{\"u}ldali AND Gregor Engels AND Markus Niehammer AND Matthias Hamburg},
  title = {Modellbasierte Bewertung von Testprozessen nach TPI NEXT® mit Gesch{\"a}ftsprozess-Mustern},
  booktitle = {Software Engineering 2013},
  year = {2013},
  editor = {Stefan Kowalewski, Bernhard Rumpe},
  pages = {331--344},
  organization = {GI},
  month = {M{\"a}rz},
  note = {Fachtagung des GI-FachbereichsSoftwaretechnik26. Februar - 1. M{\"a}rz 2013AachenProceedings},
  abstract = {Die Qualit{\"a}t eines zu entwickelnden Softwareprodukts wird entscheidend durch die Qualit{\"a}t des zugeh{\"o}rigen Textprozesses beeinflusst. Das TPI(R)- Modell ist ein Referenzmodell zur Bewertung der Qualit{\"a}t des Testprozesses, das mittels Kontrollpunkten den Reifegrad von Testaktivit{\"a}ten bestimmt.},
  series = {LNI},
  volume = {P-213}
}

@inproceedings{GE2013,
  author = {Gregor Engels},
  title = {On-the-Fly Computing - Das Entwicklungs- und Betriebsparadigma f{\"u}r Softwaresysteme der Zukunft},
  booktitle = {Software Engineering 2013},
  year = {2013},
  editor = {Stefan Kowalewski, Bernhard Rumpe},
  pages = {17--18},
  month = {M{\"a}rz},
  note = {eingeladener VortragFachtagung des GI-Fachbereichs Softwaretechnik26. Februar - 1. M{\"a}rz 2013AachenProceedings},
  journal = {LNI},
  series = {LNI},
  volume = {P-213}
}

@inproceedings{icws13,
  author = {Marie Christin Platenius AND Markus von Detten AND Christian Gerth AND Wilhelm Sch{\"a}fer AND Gregor Engels},
  title = {Service Matching under Consideration of Explicitly Specified Service Variants},
  booktitle = {IEEE 20th International Conference on Web Services (ICWS 2013)},
  year = {2013},
  publisher = {IEEE Computer Society (to appear)}
}

@inproceedings{Models2012,
  author = {Zille Huma AND Christian Gerth AND Gregor Engels AND Oliver Juwig},
  title = {Towards an Automatic Service Discovery for UML-based Rich Service Descriptions},
  booktitle = {Proceedings of the ACM/IEEE 15th International Conference on Model Driven Engineering Languages and Systems (MODELS'12)},
  year = {2012},
  pages = {709-725},
  publisher = {Springer-Verlag},
  address = {Berlin/Heidelberg},
  abstract = {Service-oriented computing (SOC) promises to solve many issues in the area of distributed software development, e.g. the realization of the loose coupling pattern in practice through service discovery and invocation. For this purpose, service descriptions must comprise structural as well as behavioral information of the services otherwise an accurate service discovery is not possible. We addressed this issue in our previous paper and proposed a UML-based rich service description language (RSDL) providing comprehensive notations to specify service requests and offers.However, the automatic matching of service requests and offers specified in a RSDL for the purpose of service discovery is a complex task, due to multifaceted heterogeneity of the service partners. This heterogeneity includes the use of different underlying ontologies or different levels of granularity in the specification itself resulting in complex mappings between service requests and offers. In this paper, we present an automatic matching mechanism for service requests and offers specified in a RSDL that overcomes the underlying heterogeneity of the service partners.},
  series = {LNCS},
  volume = {7590}
}

@inproceedings{adaptcases_seams11,
  author = {Markus Luckey AND Benjamin Nagel AND Christian Gerth AND Gregor Engels},
  title = {Adapt Cases: Extending Use Cases for Adaptive Systems},
  booktitle = {Proceeding of the 6th international symposium on Software engineering for adaptive and self-managing systems},
  year = {2011},
  pages = {30--39},
  publisher = {ACM},
  address = {New York, NY, USA},
  month = {May},
  abstract = {Adaptivity is prevalent in today's software. Mobile devices self-adapt to available network connections, washing machines adapt to the amount of laundry, etc. Current approaches for engineering such systems facilitate the specification of adaptivity in the analysis and the technical design. However, the modeling of platform independent models for adaptivity in the logical design phase remains rather neglected causing a gap between the analysis and the technical design phase. To overcome this situation, we propose an approach called Adapt Cases. Adapt Cases allow the explicit modeling of adaptivity with dedicated means, enabling adaptivity to gather attention early in the software engineering process. Since our approach is based on use cases it is easy adoptable in new and even running projects that use the UML as a specification language, and additionally, can be easily incorporated into model-based development environments. },
  series = {SEAMS '11}
}

@inproceedings{wachsmuth2011a,
  author = {Henning Wachsmuth AND Benno Stein AND Gregor Engels},
  title = {Constructing Efficient Information Extraction Pipelines},
  booktitle = {Proceedings of the 20th ACM Conference on Information and Knowledge Management},
  year = {2011},
  pages = {2237-2240},
  publisher = {ACM},
  address = {Glasgow, Scotland},
  month = {October},
  abstract = {Information Extraction (IE) pipelines analyze text through several stages. The pipeline's algorithms determine both its effectiveness and its run-time efficiency. In real-world tasks, however, IE pipelines often fail acceptable run-times because they analyze too much task-irrelevant text. This raises two interesting questions: 1) How much "efficiency potential" depends on the scheduling of a pipeline's algorithms? 2) Is it possible to devise a reliable method to construct efficient IE pipelines?Both questions are addressed in this paper. In particular, we show how to optimize the run-time efficiency of IE pipelines under a given set of algorithms. We evaluate pipelines for three algorithm sets on an industrially relevant task: the extraction of market forecasts from news articles. Using a system-independent measure, we demonstrate that efficiency gains of up to one order of magnitude are possible without compromising a pipeline's original effectiveness.}
}

@inproceedings{Soltenborn2010,
  author = {Nils Bandener AND Christian Soltenborn AND Gregor Engels},
  title = {Extending DMM Behavior Specifications for Visual Execution and Debugging},
  booktitle = {Proceedings of the 3rd International Conference on Software Language Engineering (SLE 2010)},
  year = {2011},
  editor = {B. Malloy, S. Staab, M. van den Brand},
  pages = {357--376},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Dynamic Meta Modeling (DMM) is a visual semantics specification technique targeted at behavioral languages equipped with a metamodel defining the language's abstract syntax. Given a model and a DMM specifification, a transition system can be computed which represents the semantics of that model. It allows for the investigation of the model's behavior, e.g. for the sake of understanding the model's semantics or to verify that certain requirements are fufilled. However, due to a number of reasons such as tooling and the size of the resulting transition systems, the manual inspection of the resulting transition system is cumbersome.One solution would be a visualisation of the model's behavior using animated concrete syntax. In this paper, we show how we have enhanced DMM such that visual execution and debugging can be added to a language in a simple manner.},
  series = {LNCS},
  volume = {6563}
}

@inproceedings{KGE-Caise11,
  author = {Lial Khaluf AND Christian Gerth AND Gregor Engels},
  title = {Pattern-Based Modeling and Formalizing of Business Process Quality Constraints},
  booktitle = {Proceedings of the 23rd International Conference on Advanced Information System Engineering (CAiSE'11)},
  year = {2011},
  editor = {H. Mouratidis and C. Rolland},
  pages = {521-535},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {The quality of business processes can be checked by verifying theircompliance with specific quality constraints. These constraints represent a set of required temporal and logical relationships between different steps of business processes.Quality constraints are usually formulated as informal texts, which makes themdifficult to be verified, when business processes become complex. One way tosolve this problem is by automating the verification of quality constraints onbusiness processes by applying model checking. To apply model checking, bothbusiness processes and quality constraints have to be formalized. In this paper,we define a new visual language for modeling quality constraints and we providea pattern-based translation for quality constraint models into Computation TreeLogic formulas.},
  series = {LNCS},
  volume = {6741}
}

@inproceedings{GerthSCC11,
  author = {Christian Gerth AND Markus Luckey AND Jochen K{\"u}ster AND Gregor Engels},
  title = {Precise Mappings between Business Process Models in Versioning Scenarios},
  booktitle = {Proceedings of the IEEE 8th International Conference on Services Computing (SCC'11)},
  year = {2011},
  pages = {218-225},
  publisher = {IEEE Computer Society},
  abstract = {In the development process of service-oriented systems, business process models are used at different levels. Typically, high-level business process models that describe business requirements and needs are stepwise refined to the IT level by different business modelers and software architects. As a result, different process model versions must be compared and merged by means of model version control. An important prerequisite for process model version control is an elaborated matching approach that results in precise mappings between different process model versions. The challenge of such an approach is to deal with syntactically different process models that are semantically equivalent. For that purpose, matching techniques must consider the semantics of process modeling languages. In this paper, we present a matching approach for process models in a versioning scenario. Based on a term formalization of process models, we enable an efficient and effective way to match syntactically different but semantically equivalent process models resulting in precise mappings.}
}

@inproceedings{quaasy_poster11,
  author = {Markus Luckey AND Christian Gerth AND Christian Soltenborn AND Gregor Engels},
  title = {QUAASY - QUality Assurance of Adaptive SYstems},
  booktitle = {Proceedings of the 8th International Conference on Autonomic Computing (ICAC'11)},
  year = {2011},
  publisher = {ACM},
  month = {June},
  abstract = {The emerging approach to tackle the increasing complexity of today's software systems is the use of self-adaptation techniques. Modeling and implementing adaptivity features is a burdensome and error-prone task that potentially results in erroneous system models. As a consequence, quality analysis and assurance must be considered early in the development of self-adaptive systems.We propose a quality assurance approach for self-adaptive systems in terms of an integrated modeling and analysis approach, which helps identifying errors in modeled self-adaptive systems early in the design process. We employ a modeling language for self-adaptive systems including adaptation rules and formally define their semantics. Given the language and its formal semantics, we formulate quality properties, such as fairness of the specified adaptation rule system. These quality properties are verified using a model checking approach.}
}

@inproceedings{HPRSSE-2011,
  author = {Marianne Heinemann AND Markus Palme AND Andreas Rothmann AND Frank Salger AND J{\"u}rgen Sch{\"o}nke AND Gregor Engels},
  title = {Selektionswerkzeug zur Auswahl projektspezifischer Vorgehensstrategien},
  booktitle = {Software Engineering 2011},
  year = {2011},
  editor = {R. Reussner, M. Grund, A. Oberweis, W. Tichy},
  pages = {33--36},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {Februar},
  series = {Lecture Notes in Informatics},
  volume = {P-183}
}

@inproceedings{GE2011,
  author = {Gregor Engels},
  title = {Services aus der Cloud = Fahren im Nebel? Wie minimiere ich die Risiken und erreiche hohe Qualit{\"a}t?},
  booktitle = {Proceedings der 41. Jahrestagung der Gesellschaft f{\"u}r Informatik - Informatik 2011},
  year = {2011},
  editor = {H.-U. Hei{\ss}, P. Pepper, H. Schlingloff, J. Schneider},
  publisher = {GI},
  month = {Oktober},
  note = {Informatik schafft Communities4.-7. Oktober 2011Berlin},
  abstract = {Der Kostendruck einerseits und die Verf{\"u}gbarkeit des Internets andererseits f{\"u}hren dazu, dass Softwaresysteme auf Services aus der Cloud zur{\"u}ckgreifen (m{\"u}ssen bzw. k{\"o}nnen). Dies gilt f{\"u}r alle Anwendungsbereiche und somit insbesondere auch f{\"u}r die Software im Auto. Aber wie sorge ich daf{\"u}r, dass die Services aus der Cloud zu meinem Softwaresystem passen und die Anforderungen erf{\"u}llen? Der Vortrag diskutiert aktuelle Ans{\"a}tze der konstruktiven und analytischen Qualit{\"a}tssicherung, um durch Ma{\ss}nahmen sowohl zur Entwicklungs- als auch Laufzeit eine hohe Qualit{\"a}t beim Einsatz von Services aus der Cloud zu erzielen. Insbesondere wird {\"u}ber aktuelle Arbeiten im neuen DFG Sonderforschungsbereich 901 "On-the-Fly Computing" berichtet.},
  series = {LNI},
  volume = {192}
}

@inproceedings{EK2011,
  author = {Gregor Engels AND Marion Kremer},
  title = {Situational Software Engineering: Ein Rahmenwerk f{\"u}r eine situationsgerechte Auswahl von Entwicklungsmethoden und Vorgehensmodellen},
  booktitle = {Proceedings der41. Jahrestagung der Gesellschaft f{\"u}r Informatik - Informatik 2011;},
  year = {2011},
  editor = {H.-U. Hei{\ss}, P. Pepper, H. Schlingloff, J. Schneider},
  publisher = {GI},
  month = {Oktober},
  note = {Informatik schafft Communities4.-7. Oktober 2011Berlin},
  abstract = {Industrielle Softwareentwicklung unterliegt einem stetig steigenden Kosten-, Zeit- und Qualit{\"a}tsdruck, der einen effektiven, effizienten und wirtschaftlichen Einsatz der zur Verf{\"u}gung stehenden Ressourcen bei IT Dienstleistern erfordert. In diesem Beitrag berichten wir {\"u}ber industrielle Erfahrungen bei der Entwicklung eines Rahmenwerks, um f{\"u}r ein aktuelles Softwareprojekt im Sinne eines Situational Software Engineering eine situationsgerechte Auswahl und Kombination von Methoden und Vorgehensmodellbausteinen zu bestimmen. Es werden konkrete Kriterien angegeben, anhand deren Methodenb{\"u}ndel f{\"u}r Systemklassen geschn{\"u}rt werden k{\"o}nnen.},
  series = {LNI},
  volume = {192}
}

@inproceedings{Christ2010,
  author = {Fabian Christ AND Jan-Christopher Bals AND Gregor Engels AND Christian Gerth AND Markus Luckey},
  title = {A Generic Meta-Model-based Approach for Specifying Framework Functionality and Usage},
  booktitle = {Proceedings of the 48th International Conference on Objects, Models, Components and Patterns (TOOLS'10), M{'a}laga (Spain)},
  year = {2010},
  editor = {J. Vitek},
  pages = {21--40},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {June},
  abstract = {Enterprise software development is based on the usage of frameworks. However, well-established concepts to specify framework functionality and how to use it can hardly be found. As consequence, there are poor framework documentations. Various problems arise from this, e.g. a high effort for learning a framework and therefore the need of framework specialists. Existing framework description languages (FDL) focus on parts of the problem but do not cover all aspects of specifying framework functionality and usage. In this paper, we present a generic approach for specifying all aspects of framework functionality and usage. We collected requirements to identify relevant aspects and defined a generic meta-model for FDLs. The generic meta-model is the base for defining concrete FDLs while guaranteeing that all relevant framework aspects are covered. Particularly, due to its generic character, parts of the meta-model representing specific framework aspects can be instantiated by existing or newly defined languages.},
  journal = {LNCS},
  series = {LNCS},
  volume = {6141}
}

@inproceedings{ES10,
  author = {Gregor Engels AND Stefan Sauer},
  title = {A Meta-Method for Defining Software Engineering Methods},
  booktitle = {Graph Transformations and Model-Driven Engineering},
  year = {2010},
  editor = {G. Engels, C. Lewerentz, W. Sch{\"a}fer, A. Sch{\"u}rr, B. Westfechtel},
  pages = {411--440},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  journal = {LNCS},
  series = {LNCS},
  volume = {5765}
}

@inproceedings{SEH10,
  author = {Frank Salger AND Gregor Engels AND Alexander Hofmann},
  title = {Assessments in Global Software Development: A Tailorable Framework for Industrial Projects},
  booktitle = {Proceedings ACM/IEEE 32nd International Conference on Software Engineering, Software Engineering in Practice Track, Cape Town, South Africa (ICSE'10)},
  year = {2010},
  editor = {W. Visser, I. Kr{\"u}ger},
  pages = {29--38},
  publisher = {ACM New York, NY, USA},
  month = {May},
  abstract = {Assessments are an effective technique for software quality assurance. As global software development (GSD) becomes the standard, an assessment framework must be flexible to support different sourcing and shoring models. Although much work exists on inspections and reviews, an assessment framework which addresses these challenges is missing. We present a systematic yet flexible assessment framework. The paper contributes: i) The description of our assessment framework which addresses four challenges: Appropriateness of a software requirements specification (SRS), viability of software architectures and SRS, wholeness of work packages, and compliance of results with predefined quality objectives. ii) A detailed explanation how the assessment framework can be tailored to support offshore and outsourcing scenarios. This paper describes the result of a two years research initiative at Capgemini sd\&m and serves the practitioner to implement assessment frameworks according to his needs. We also discuss open research questions of high relevance for the software industry.},
  volume = {2}
}

@inproceedings{HE10,
  author = {Marianne Heinemann AND Gregor Engels},
  title = {Auswahl projektspezifischer Vorgehensstrategien},
  booktitle = {Integration von Vorgehensmodellen und Projektmanagement},
  year = {2010},
  editor = {O. Linssen, T. Greb, M. Kuhrmann, D. Lange, R. H{\"o}hn},
  pages = {132--142},
  publisher = {Shaker Verlag},
  month = {April}
}

@inproceedings{GerthSCC10,
  author = {Christian Gerth AND Markus Luckey AND Jochen K{\"u}ster AND Gregor Engels},
  title = {Detection of Semantically Equivalent Fragments for Business Process Model Change Management},
  booktitle = {Proceedings of the IEEE 7th International Conference on Services Computing (SCC'10)},
  year = {2010},
  pages = {57--64},
  publisher = {IEEE Computer Society},
  note = {Best Student Paper of SCC 2010.},
  abstract = {Modern business process modeling environments support distributed development by means of model version control, i. e., comparison and merging of two different model versions. This is a challenging task since most modeling languages support an almost arbitrary creation of process models. Thus, in multi-developer environments, process models or parts of them are often syntactically very different but semantically equivalent. Hence, the comparison of business process models must be performed on a semantic level rather then on a syntactic level. For the domain of business process modeling, this problem is yet unsolved.This paper describes an approach that allows the semantic comparison of different business process models using a normal form. For that purpose, the process models are fully automatically translated into process model terms and normalized using a term rewriting system. The resulting normal forms can be efficiently compared and easily be used for reconciliation. Our approach enables the semantic comparison of business process models ignoring syntactic redundancies.}
}

@inproceedings{KuesterGE10,
  author = {Jochen K{\"u}ster AND Christian Gerth AND Gregor Engels},
  title = {Dynamic Computation of Change Operations in Version Management of Business Process Models},
  booktitle = {Proceedings of the 6th European Conference on Modelling Foundations and Applications (ECMFA'10)},
  year = {2010},
  editor = {T. K{\"u}hne, B. Selic},
  pages = {201--216},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {June},
  abstract = {Version management of business process models requires that changescan be resolved by applying change operations. In order to give a user maximalfreedom concerning the application order of change operations, position parameters of change operations must be computed dynamically during change resolution. In such an approach, change operations with computed position parameters must be applicable on the model and dependencies and conflicts of change operations must be taken into account because otherwise invalid models can be constructed. In this paper, we study the concept of partially specified change operations where parameters are computed dynamically. We provide a formalization for partially specified change operations using graph transformation and provide a concept for their applicability. Based on this, we study potential dependencies and conflicts of change operations and show how these can be taken into account within change resolution. Using our approach, a user can resolve changes of business process models without being unnecessarily restricted to a certain order.},
  series = {LNCS},
  volume = {6138}
}

@inproceedings{SchaeferBirattariBloemerDorigo+2010,
  author = {Wilhelm Sch{\"a}fer AND Mauro Birattari AND Johannes Bl{\"o}mer AND Marco Dorigo AND Gregor Engels AND Rehan O'Grady AND Marco Platzner},
  title = {Engineering Self-Coordinating Software Intensive Systems},
  booktitle = {Proceedings of the FSE/SDP Workshop on the Future of Software Engineering Research (FoSER '10)},
  year = {2010},
  pages = {321--324},
  publisher = {Association for Computing Machinery (ACM)}
}

@inproceedings{HDE10,
  author = {Marianne Heinemann AND Bettina Duwe AND Gregor Engels},
  title = {Enriching RUP with key success factors for large-scale custom software development projects},
  booktitle = {Software \& Systems Engineering Essentials (SEE) 2010},
  year = {2010},
  editor = {M. Sihling, A. Rausch, J. Friedrich, M. Kuhrmann},
  pages = {37--56},
  publisher = {Technische Universit{\"a}t M{\"u}nchen},
  month = {Mai},
  abstract = {Capgemini sd\&m has a long-standing experience in executing custom software development (CSD) projects with a special focus on large-scale and rightshore projects, where resources are distributed over different locations in Germany, Poland (nearshoring) or India (farshoring).For many years, that experience was brought together in a proprietary life cycle model for CSD projects. However, this proprietary life cycle model was not based on an existing industrial standard and therefore was difficult to communicate to clients as well as to employees with other cultural background.Besides the proprietary life cycle model, Capgemini sd\&m has developed its software engineering methodology named QUASAR that focuses on the special requirements for Enterprise Architecture and Custom Software Development projects. With having enhanced QUASAR at fast pace in the last years, it became important to not only update the life cycle model, but to additionally integrate the software engineering methodology.With the continuously increasing trend to software industrialization and thus the growing demand for standardization, the goal was to build on a standard life cycle model and integrate the key factors of our successful software engineering methodology QUASAR.2 ApproachTo unify the understanding of our software engineering processes and work products, we defined an ontology of relevant software engineering notions as the basis for all further actions.The RUP disciplines have been validated, and we found a need to extend and detail them in order to reflect the special requirements of custom software development.Next step was to validate the work products. A fine-grained artifact model has been developed that elaborates the artifact hierarchy based on a categorization for different artifact types. The result is a comprehensive catalogue of artifacts for all software engineering disciplines. We identified the critical artifacts and defined relevant in- and output artifacts for each discipline.In parallel to the development of the artifact model, we commenced the life cycle model evolution. We identified the key success factors of our traditional approach and substantiated RUP to explicitly reflect them.We elaborated our life cycle model based on the three dimensions results, time and tasks, the latter being reflected by the RUP concepts of phases, disciplines and activities. The results dimension was one elementary pillar within our traditional model: We work with a concept of stages that coarsely define, to which degree the system has been built. The explicit definition of development stages allows parallelized work and thus a quicker project execution.The approach to build a development stage is iterative, where cycling through the development activities occurs by component and includes testing and software integration. The resulting step-by-step integration of software from early on is seen as a further success factor within our traditional life cycle model and as such has been transferred to the new model.The bridging element between the life cycle model and the software engineering methodology is a new kind of milestone that is not foreseen by RUP: the discipline milestone. These milestones define the to-be status of critical artifacts at special points in time for each discipline and based on our development stages.The resulting life cycle model is called ``Quasar project incremental'' and is meant to be our standard life cycle model for large-scale and rightshore projects.3 Evaluation``Quasar project incremental'' combines the standard RUP approach with our traditional key success factors for custom software development. Furthermore, it integrates project management with our software engineering methodology hence providing a comprehensive model of interaction of those two levels within one project that practically helps to communicate.In the meantime, ``Quasar project incremental'' has been deployed in several custom software development projects. Concrete samples and a critical evaluation will be given in the presentation.},
  series = {TUM-I1009}
}

@inproceedings{ELSSW210,
  author = {Gregor Engels AND Claus Lewerentz AND Wilhelm Sch{\"a}fer AND Andy Sch{\"u}rr AND Bernhard Westfechtel},
  title = {Graph Transformations and Model-Driven Engineering: The Merits of Manfred Nagl},
  booktitle = {Graph Transformations and Model-Driven Engineering},
  year = {2010},
  editor = {G. Engels, C. Lewerentz, W. Sch{\"a}fer, A. Sch{\"u}rr, B. Westfechtel},
  pages = {1--5},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  journal = {LNCS},
  series = {LNCS},
  volume = {5765}
}

@inproceedings{ES10,
  author = {Gregor Engels AND Frank Salger},
  title = {Knowledge Transfer in Global Software Development - Leveraging Acceptance Test Case Specifications},
  booktitle = {In Proceedings of the ACM/IEEE 32nd International Conference on Software Engineering (ICSE), New Ideas and Emergent Results program, May 2010, Cape Town (South Africa)},
  year = {2010},
  pages = {211--214},
  publisher = {ACM New York, NY, USA},
  abstract = {Effective knowledge transfer (KT) is always important in software development projects, but crucial in global software development (GSD). Two challenges arise: First, reviews of the software requirements specification (SRS) are indispensable, but not always effective. Second, using knowledge representations that support KT from customers to developers is paramount. However, 'classical' SRS often don't support SRS comprehension of all stakeholders. We address these two challenges with a new approach that exploits the multi-fold power of a acceptance test case specifications (ATC-Specs): 1) A specific two-stage test-based review technique is used. We argue that these two-stage reviews of ATC-Specs increase the quality of the ATC-Specs and the SRS. 2) Additionally to the SRS, ATC-Specs are delivered to the offshore team, bridging the mental models of different stakeholders, and thus effectively transferring knowledge. We provide preliminary evidence of the validity of our approach based on a commercial GSD project at Capgemini sd\&m.}
}

@inproceedings{GerthModels10,
  author = {Christian Gerth AND Jochen K{\"u}ster AND Markus Luckey AND Gregor Engels},
  title = {Precise Detection of Conflicting Change Operations using Process Model Terms},
  booktitle = {Proceedings of the ACM/IEEE 13th International Conference on Model Driven Engineering Languages and Systems (MODELS'10)},
  year = {2010},
  editor = {D.C. Petriu, N. Rouquette, and {\O}. Haugen},
  pages = {93--107},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  note = {ACM Distinguished Paper Award MODELS 2010.},
  abstract = {Version management of process models requires that changes can be resolved by applying change operations. Conflict detection is an important part of version management and the minimization of the number of detected conflicts also reduces the overhead when resolving changes. As not every syntactic conflict leads to a conflict when taking into account model semantics, a computationof conflicts solely on the syntax leads to an unnecessary high number of conflicts. In this paper, we introduce the notion of syntactic and semantic conflicts for change operations of process models. We provide a method how to efficiently compute conflicts, using a term formalization of process models. Using this approach, we can significantly reduce the number of overall conflicts and thereby reduce the amount of work for the user when resolvingconflicts.},
  series = {LNCS},
  volume = {6395}
}

@inproceedings{Baumann2009,
  author = {Andrea Baumann AND Gregor Engels AND Alexander Hofmann AND Stefan Sauer AND Johannes Willkomm},
  title = {A Holistic Software Engineering Method for Service-Oriented Application Landscape Development},
  booktitle = {Proceedings of the First NAF Academy Working Conference on Practice-Driven Research on Enterprise Transformation (PRET 2009), Amsterdam (The Netherlands)},
  year = {2009},
  pages = {1--17},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Enterprises are transforming into enterprises which follow from a business as well as from an IT perspective a service-oriented paradigm. This change towards service-oriented enterprise and IT architectures has to be reflected in the methodologies of developing whole application landscapes as well as individual applications. Quasar (Quality Software Architecture) has been developed as the standard architecture and development method of Capgemini sd\&m for individual applications. For the development of service-oriented enterprise application landscapes, Quasar Enterprise has been designed. Both Quasar and Quasar Enterprise are integrated with each other within a holistic software engineering method to seamlessly cover the full development lifecycle of service-oriented application landscapes, from business modeling and service design to actual software development. In this paper, we illustrate how a company-wide ontology of development artifacts serves as the key feature for integrating both methods.},
  series = {Lecture Notes in Business Information Processing},
  volume = {28}
}

@inproceedings{ECMDA-09,
  author = {Jochen K{\"u}ster AND Christian Gerth AND Gregor Engels},
  title = {Dependent and Conflicting Change Operations of Process Models},
  booktitle = {Proceedings of the 5th European Conference on Model-Driven Architecture Foundations and Applications (ECMDA-FA'09)},
  year = {2009},
  pages = {158--173},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Version management of models is common for structural diagrams such as class diagrams but still challenging for behavioral models such as process models. For process models, conflicts of change operations are difficult to resolve because often dependencies to other change operations exist. As a consequence, conflicts and dependencies between change operations must be computed and shown to the user who can then take them into account while creating a consolidated version. In this paper, we introduce the concepts of dependencies and conflicts of change operations for process models and provide a method how to compute them. We then discuss different possibilities for resolving conflicts. Using our approach it is possible to enable version management of process models with minimal manual intervention of the user.},
  series = {LNCS},
  volume = {5562}
}

@inproceedings{wuebb2009,
  author = {Martin Assmann AND Gregor Engels AND Thomas von der Ma{\ss}en AND Andreas W{\"u}bbeke},
  title = {Identifying Software Product Line Component Services},
  booktitle = {Proceedings of International Conference on Evaluation of Novel Approaches to Software Engineering (ENASE 09)},
  year = {2009},
  editor = {S. Jablonski, L. Maciaszek},
  pages = {45--56},
  abstract = {Software Product Line (SPL) development provides the possibility of reusing common parts in similar software products. However the SPL approach does not centrally improve the maintenance of software products of a Software Product Line. This paper presents an approach for reducing maintenance costs of SPL products by using the concept Software as a Service. The SPL-SaaS approach was developed with the experiences of arvato services integrating the software product line concept since years. It shows up the advantageous and disadvantageous characteristics of components that play a role for the concept combination. To be able to identify adequate components, criteria for the identification of software components suitable for the approach are derived from these characteristics. Furthermore the requirements of the potential service users are examined and categorized concerning their effects on the system architecture. Special requirements of customers often lead to architectural constraints that are not compatible with the approach. If both, the criteria are met and the architectural constraints are compatible, the SPL-SaaS approach can be applied to a component. The whole approach is applied on an example of arvato services}
}

@inproceedings{Soltenborn2009b,
  author = {Gregor Engels AND Daniela Fisseler AND Christian Soltenborn},
  title = {Improving Reusability of Dynamic Meta Modeling Specifications with Rule Overriding},
  booktitle = {Proceedings of the 2009 IEEE Symposium on Visual Languages and Human-Centric Computing (VL/HCC 2009), Corvallis, Oregon (USA)},
  year = {2009},
  editor = {R. DeLine, M. Minas, M. Erwig},
  pages = {39--46},
  publisher = {IEEE Computer Society},
  address = {Piscataway, NJ (USA)},
  note = {Best Paper of VL/HCC 2009.},
  abstract = {Dynamic Meta Modeling (DMM) is a visual semantics specification technique targeted at languages equipped with a metamodel. In DMM, the metamodel of a language is mapped into a runtime metamodel able to express runtime states of instances of that language. In addition, graph transformation rules are defined which describe how these runtime states change in time. Given an instance of the runtime metamodel and a set of rules typed over that metamodel, a transition system can be computed which represents the semantics of the model instance under investigation.To be easily understandable by language engineers, DMM resembles a couple of well-known object-oriented concepts. Part of this is the fact that a DMM rule has many similarities to a method in an object-oriented language.In this paper, we enhance DMM such that DMM rules can "override" other DMM rules, similar to a method being overridden in a subclass. We argue that this does not only have positive impact on reusability of DMM specifications, but also improves the intuitive understandability of DMM rules.}
}

@inproceedings{EngSaSa09,
  author = {Frank Salger AND Stefan Sauer AND Gregor Engels},
  title = {Integrated Specification and Quality Assurance for Large Business Information Systems},
  booktitle = {Proceedings of the 2nd India Software Engineering Conference (ISEC'09)},
  year = {2009},
  pages = {129--130},
  publisher = {ACM Press},
  address = {New York, NY, USA}
}

@inproceedings{GerthModels09,
  author = {Christian Gerth AND Jochen K{\"u}ster AND Gregor Engels},
  title = {Language-Independent Change Management of Process Models},
  booktitle = {Proceedings of the ACM/IEEE 12th International Conference on Model Driven Engineering Languages and Systems (MODELS'09). Denver (CO, USA)},
  year = {2009},
  editor = {A. Sch{\"u}rr, B. Selic},
  pages = {152--166},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {In model-driven development approaches, process models are used at different levels of abstraction and are described by different languages. Similar to other software artifacts, process models are developed in team environments and underlie constant change. This requires reusable techniques for the detection of changes between different process models and the computation of dependencies and conflicts between changes. In this paper, we propose a framework for the construction of process model change management solutions that provides generic techniques for the detection of differences and the computation of dependencies and conflicts between changes. The framework contains an abstract representation for process models that serves as a common denominator for different process models. In addition, we show how the framework is instantiated exemplarily for BPMN.},
  series = {LNCS},
  volume = {5795 }
}

@inproceedings{seaa09/mde,
  author = {Baris G{\"u}ldali AND Michael Mlynarski AND Andreas W{\"u}bbeke AND Gregor Engels},
  title = {Model-Based System Testing Using Visual Contracts},
  booktitle = {Proceedings of Euromicro SEAA Conference 2009, Special Session on ``Model Driven Engineering''},
  year = {2009},
  pages = {121-124},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  abstract = {In system testing the system under test (SUT) is tested against high-level requirements which are captured at early phases of the development process. Logical test cases developed from these requirements must be translated to executable test cases by augmenting them with implementation details. If manually done these activities are error-prone and tedious. In this paper we introduce a model-based approach for system testing where we generate first logical test cases from use case diagrams which are partially formalized by visual contracts, and then we transform these to executable test cases using model transformation. We derive model transformation rules from the design decisions of developers.}
}

@inproceedings{gse+09,
  author = {Baris G{\"u}ldali AND Holger Funke AND Michael Jahnich AND Stefan Sauer AND Gregor Engels},
  title = {Semi-automated Test Planning for e-ID Systems by Using Requirements Clustering},
  booktitle = {24th IEEE/ACM International Conference on Automated SoftwareEngineering (ASE 2009), 16-20 November 2009, Auckland, New Zeland},
  year = {2009},
  pages = {29-39},
  abstract = {In acceptance testing, customer requirements as specified in system specifications have to be tested for their successful implementation. This is a time-consuming task due to inherent system complexity and thus a large number of requirements. In order to reduce efforts in acceptance testing, we introduce a novel approach that exploits redundancies and implicit relations in requirements specifications, which are based on multi-viewpoint techniques, in our case the reference model for open distributed processing (RM-ODP). It deploys requirements clustering and linguistic analysis techniques for reducing the total number of test cases. We report on concrete experiences with this approach within joint R\&D work of the Software Quality Lab (s-lab) of the University of Paderborn and HJP Consulting, an international consulting company, specialized in planning, procurement and acceptance testing of national electronic identification (e-ID) systems. The paper is concluded with an overview on the current tool support especially for automated detection of the redundancies and implicit relations in requirements. Also the future work on the tool support for the overall test specification process is discussed. }
}

@inproceedings{EGPS09,
  author = {Gregor Engels AND Silke Geisen AND Stefan Sauer AND Olaf Port},
  title = {Sicherstellen der Betrachtung von nicht-funktionalen Anforderungen in SCRUM-Prozessen durch Etablierung von Feedback},
  booktitle = {Informatik 2009 - Im Focus das Leben},
  year = {2009},
  editor = {S. Fischer, E. Maehle, R. Reischuk},
  pages = {458},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  series = {Lecture Notes in Informatics},
  volume = {154}
}

@inproceedings{Soltenborn2009a,
  author = {Christian Soltenborn AND Gregor Engels},
  title = {Towards Test-Driven Semantics Specification},
  booktitle = {Proceedings of the 12th International Conference on Model Driven Engineering Languages and Systems (MODELS 2009), Denver, Colorado (USA)},
  year = {2009},
  editor = {A. Sch{\"u}rr, B. Selic},
  pages = {378--392},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Behavioral models are getting more and more important within the software development cycle. To get the most use out of them, their behavior should be defined formally. As a result, many approaches exist which aim at specifying formal semantics for behavioral languages (e.g., Dynamic Meta Modeling (DMM), Semantic Anchoring). Most of these approaches give rise to a formal semantics which can e.g. be used to check the quality of a particular language instance, for instance using model checking techniques.However, if the semantics specification itself contains errors, it is more or less useless, since one cannot rely on the analysis results. Therefore, the language engineer must make sure that the semantics he develops is of the highest quality possible. To help the language engineer to achieve that goal, we propose a test-driven semantics specification process: the semantics of the language under consideration is first informally demonstrated using example models, which will then be used as test cases during the actual semantics specification process. In this paper, we present this approach using the already mentioned specification language DMM.},
  series = {LNCS},
  volume = {5795}
}

@inproceedings{Engels08-1,
  author = {Gregor Engels AND Andreas Hess AND Bernhard Humm AND Oliver Juwig AND Marc Lohmann AND Jan-Peter Richter AND Markus Vo{\ss} AND Johannes Willkomm},
  title = {A Method for Engineering a true Service-Oriented Architecture},
  booktitle = {Proceedings of the Tenth International Conference on Enterprise Information Systems (ICEIS 2008), Barcelona (Spain)},
  year = {2008},
  editor = {J. Cordeiro, J. Filipe},
  pages = {272--281},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {June },
  note = {10th International Conference on Enterprise Information Systems (ICEIS 2008)},
  volume = {ISAS-2}
}

@inproceedings{Engels08,
  author = {Gregor Engels AND Baris G{\"u}ldali AND Christian Soltenborn AND Heike Wehrheim},
  title = {Assuring Consistency of Business Process Models and Web Services using Visual Contracts},
  booktitle = {Proceedings of the 3rd International Symposium on Applications of Graph Transformation with Industrial Relevance (AGTIVE 2007), Kassel (Germany)},
  year = {2008},
  editor = {A. Sch{\"u}rr, M. Nagl, A. Z{\"u}ndorf},
  pages = {17--31},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  abstract = {Business process models describe workflows by a set of actions together with their ordering. When implementing business processes within a service-oriented architecture, these actions are mapped to existing IT (web) services, which are then to be executed in the order specified by the business process. However, the execution of a web service can require certain preconditions to be fulfilled. These might not hold at the time of execution specified in the business process model: it can be inconsistent with the web service specification.In this paper we propose a technique for checking consistency of process models with web service specifications. To this end, both are equipped with a formal semantics (in terms of graph transformations). We show how to use an existing model checker for graph transformation systems to carry out the consistency check.},
  series = {LNCS},
  volume = {5088}
}

@inproceedings{Comp08,
  author = {Frank Salger AND Marcel Bennicke AND Gregor Engels AND Claus Lewerentz},
  title = {Comprehensive Architecture Evaluation and Management in Large Software-Systems},
  booktitle = {Quality of Software Architectures. Models and Architectures},
  year = {2008},
  editor = {S. Becker, F. Plasil, R. Reussner},
  pages = {205--219},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  abstract = {The architecture of a software system is both a success and a failure factor. Taking the wrong architectural decisions may break a project, since such errors are often systematic and affect cross-cutting aspects of the system to be built. Moreover, software projects get more and more challenging due to the rising complexity and dynamics of business processes, large team size and distributed development. As the software architecture is the common platform for many project activities, it constitutes a critical success factor. Thus, a comprehensive method for evaluating a software architecture and propagating important properties of it downstream to code is needed. At sd\&m, we designed a comprehensive architecture evaluation and management framework in order to satisfy these needs. In this paper, we derive a list of requirements, such a framework should fulfill. We then present the components of our architecture evaluation method and demonstrate, how it fulfills these requirements.},
  journal = {LNCS},
  series = {LNCS},
  volume = {5281}
}

@inproceedings{DetKGFE08,
  author = {Jochen K{\"u}ster AND Christian Gerth AND Alexander F{\"o}rster AND Gregor Engels},
  title = {Detecting and Resolving Process Model Differences in the Absence of a Change Log},
  booktitle = {Proceedings of the 6th International Conference on Business Process Management (BPM'08)},
  year = {2008},
  editor = {M. Dumas, M. Reichert, M.-C. Shan},
  pages = {244--260},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Business-driven development favors the construction of process models at different abstraction levels and by different people. As a consequence, there is a demand for consolidating different versions of process models by detecting and resolving differences. Existing approaches rely on the existence of a change log which logs the changes when changing a process model. However, in several scenarios such a change log does not exist and differences must be identified by comparing process models before and after changes have been made. In this paper, we present our approach to detecting and resolving differences between process models, in the absence of a change log. It is based on computing differences and deriving change operations for resolving differences, thereby providing a foundation for variant and version management in these cases.},
  series = {LNCS},
  volume = {5240}
}

@inproceedings{VE08-2,
  author = {Hendrik Voigt AND Gregor Engels},
  title = {Ein verfeinerter GQM-Ansatz zur Qualit{\"a}tsbewertung von Software-Modellen},
  booktitle = {Proceedings of Software-Qualit{\"a}tsmodellierung und -bewertung (SQMB '08), M{\"u}nchen, Germany},
  year = {2008},
  editor = {S. Wagner, M. Broy, F. Deissenboeck, J. M{\"u}nch, P. Liggesmeyer},
  pages = {39--46},
  publisher = {Technische Universit{\"a}t M{\"u}nchen},
  abstract = {Wir stellen einen Qualit{\"a}tsmanagementansatz zur Bewertung von Software-Modellen vor. Unser Ansatz basiert auf der Goal Question Metric (GQM). Wir verfeinern GQM und f{\"u}gen wichtige Konzepte und Aktivit{\"a}ten hinzu, um auf diese Weise die Besonderheiten bei der Qualit{\"a}tsbewertung von Software-Modellen ber{\"u}cksichtigen zu k{\"o}nnen. Dabei konzentrieren wir uns insbesondere auf den Kontext eines Software-Modells als entscheidenden Einflussfaktor f{\"u}r die Dokumentation von Informationsbed{\"u}rfnissen, Qualit{\"a}tsverst{\"a}ndnis, Messung und Analyse. Aktuell wird eine Werkzeugunterst{\"u}tzung f{\"u}r die Eclipse Plattform entwickelt, damit unser Qualit{\"a}tsmanagementansatz evaluiert und wirtschaftlich eingesetzt werden kann.}
}

@inproceedings{Engels08-2,
  author = {Gregor Engels AND Anneke Kleppe AND Arend Rensink AND Maria Semenyak AND Christian Soltenborn AND Heike Wehrheim},
  title = {From UML Activities to TAAL - Towards Behaviour-Preserving Model Transformations},
  booktitle = {Proceedings of the 4th European Conference on Model Driven Architecture - Foundations and Applications (ECMDA-FA 2008), Berlin (Germany)},
  year = {2008},
  editor = {I. Schieferdecker, A. Hartman},
  pages = {95--109},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {July},
  abstract = {Model transformations support a model-driven design by providing an automatic translation of abstract models into more concrete ones, and eventually program code. Crucial to a successful application of model transformations is their correctness, in the sense that the meaning (semantics) of the models is preserved. This is especially important if the models not only describe the structure but also the intended behaviour of the systems. Reasoning about and showing correctness is, however, often impossible as the source and target models typically lack a precise definition of their semantics.In this paper, we take a first step towards provably correct behavioural model transformations. In particular, we develop transformations from UML Activities (which are visual models) to programs in TAAL, which is a textual Java-like programming language. Both languages come equipped with formal behavioural semantics, which, moreover, have the same semantic domain. This sets the stage for showing correctness, which in this case comes down to showing that the behaviour of every (well-formed) UML Activity coincides with that of the corresponding TAAL program, in a well-defined sense.},
  series = {LNCS},
  volume = {5095}
}

@inproceedings{VE08-1,
  author = {Hendrik Voigt AND Gregor Engels},
  title = {Kontextsensitive Qualit{\"a}tsplanung f{\"u}r Software-Modelle},
  booktitle = {Proceedings of Modellierung (2008), Berlin (Germany)},
  year = {2008},
  editor = {T. K{\"u}hne, W. Reisig, F. Steimann},
  pages = {165--180},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {March},
  abstract = {Der Goal Question Metric (GQM) Ansatz stellt eine allgemeine Qualit{\"a}tsmanagementstrategie dar und ber{\"u}cksichtigt infolgedessen nicht die Besonderheiten von Software-Modellen. Wir haben eine kontextsensitive Qualit{\"a}tsplanung f{\"u}r Software- Modelle entwickelt, die den GQM-Ansatz auf die Qualit{\"a}tsplanung von Software- Modellen zuschneidet und um Konzepte und Aktivit{\"a}ten erweitert. Dabei konzentrieren wir uns auf den Kontext eines Software-Modells als entscheidenden Einflussfaktor f{\"u}r die Dokumentation von Informationsbed{\"u}rfnissen, Qualit{\"a}tsverst{\"a}ndnis und Messung. Unser Ansatz zur Qualit{\"a}tsplanung besteht aus einem Metamodell zur Formulierung relevanter Inhalte und einem Prozess, der als Leitfaden bei der Planung dient.},
  series = {Lecture Notes in Informatics},
  volume = {127}
}

@inproceedings{VGE08,
  author = {Hendrik Voigt AND Baris G{\"u}ldali AND Gregor Engels},
  title = {Quality Plans for Measuring the Testability of Models},
  booktitle = {Proceedings of the 11th International Conference on Quality Engineering in Software Technology (CONQUEST 2008), Potsdam (Germany)},
  year = {2008},
  editor = {I. Schieferdecker, S. Goericke},
  pages = {353--370},
  publisher = {dpunkt.verlag},
  abstract = {For models used in model-based testing, the evaluation of their testability is an important issue. Existing approaches lack some relevant aspects for a systematic and comprehensive evaluation. Either they do (1) not consider the context of software models, (2) not offer a systematic process for selecting and developing right measurements, (3) not define a consistent and common quality understanding, or (4) not distinct between objective and subjective measurements.We present a novel quality management approach for the evaluation of software models in general that considers all these aspects in an integrated way. Our approach is based on a combination of the Goal Question Metric (GQM) and quality models. We demonstrate our approach by systematically developing a short quality plan for measuring the testability of software models.}
}

@inproceedings{DBLP:conf/se/EngelsV08,
  author = {Gregor Engels AND Markus Vo{\ss}},
  title = {Quasar Enterprise - Anwendungslandschaften serviceorientiert gestalten},
  booktitle = {Software Engineering 2008. Fachtagung des GI-Fachbereichs Softwaretechnik},
  year = {2008},
  editor = {K. Herrmann, B. Bruegge},
  pages = {24--27},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {February },
  series = {Lecture Notes in Informatics},
  volume = {121}
}

@inproceedings{Frohnhoff08,
  author = {Stephan Frohnhoff AND Gregor Engels},
  title = {Revised Use Case Point Method - Effort Estimation in Development Projects for Business Applications},
  booktitle = {Setting Quality Standards, Proceedings of the 11th International Conference on Quality Engineering in Software Technology (CONQUEST 2008), Potsdam (Germany)},
  year = {2008},
  editor = {I. Schieferdecker, S. Goericke},
  pages = {15--32},
  publisher = {dpunkt Verlag},
  abstract = {Rapid and precise effort estimation of software development projects is crucial in ITindustry. In a case study, the Use Case Point (UCP) method was applied to 15 commercialsoftware development projects. The estimated efforts were compared with the incurredproject efforts. We measured a standard deviation of 42 \%. This is not acceptablefor industrial usage. Therefore, we propose appropriate improvements of the UseCase Point method leading to significantly higher estimation accuracy with only 20 \%standard deviation. The contribution of this paper is a detailed description of the improvedUse Case Point method.}
}

@inproceedings{AssEDOC08,
  author = {Martin Assmann AND Gregor Engels},
  title = {Service-Oriented Enterprise Architectures: Evolution of Concepts and Methods},
  booktitle = {Proc. of the 12th IEEE International Enterprise Distributed Object Computing Conference 2008 (EDOC 08), Munich (Germany)},
  year = {2008},
  pages = {xxxiv--xliii},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  month = {September},
  abstract = {This paper depicts the evolution of enterprise architectures to their today often used service-oriented form and presents a state-of-the-art development process for this kind of architecture. The development process covers both the development of business architecture as well as the appropriate software architecture. While showing up a possible form of further evolution of enterprise architectures, we identify the major challenges for future development methods of enterprise architectures.}
}

@inproceedings{AssmannEcsa08,
  author = {Martin Assmann AND Gregor Engels},
  title = {Transition to Service-Oriented Enterprise Architecture},
  booktitle = {Proceedings of the Second European Conference on Software Architecture (ECSA 2008), Paphos (Cyprus)},
  year = {2008},
  editor = {R. Morrison, D. Balasubramaniam, K. E. Falkner},
  pages = {346--349},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {September},
  abstract = {Enterprise Architecture (EA) has undergone many changes since the IT has found its way into enterprises. At the moment the Service-Oriented Architecture (SOA) is being hyped but has also gained some importance. Implementing SOA can have many implications for an enterprise, depending on how visionary the implemented architecture is. This paper provides the description of an enterprise architecture that is fully-fledged concerning service-orientation and points out the architectural challenges that have to be mastered with future research results.},
  series = {LNCS},
  volume = {5292}
}

@inproceedings{Schattkowsky2007a,
  author = {Tim Schattkowsky AND Gregor Engels AND Alexander F{\"o}rster},
  title = {A Model-Based Approach for Platform-Independent Binary Components with Precise Timing and Fine-Grained Concurrency},
  booktitle = {Proceedings of the 40th Annual Hawaii International Conference on System Sciences (HICSS 2007)},
  year = {2007},
  pages = {286ff.},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  abstract = {Fine grained concurrency and accurate timing can be essential for embedded hardware and software systems. These requirements should be reflected in the specification and must be consistently enforced by the actual implementation. Automated synthesis of the implementation from such specifications appears to be a straightforward way to ensure this consistency. However, especially for software systems this is quite difficult, since software lacks the inherent timing and concurrency of a hardware system. Still, the same timing and concurrency requirements have to be fulfilled. Thus, we introduce a UML-based design approach that supports the synthesis of embedded hardware or software systems from essentially the same abstract specification. Our approach provides explicit support for specifying fine grained concurrency and microsecond accurate timing. In our approach, these properties must be ensured by the automatically derived implementation. Since this is especially hard to achieve for software systems, this paper focuses on execution on software platforms. For this, we introduce our UML Virtual Machine (UVM). It enables the direct execution of binary encoded system specifications and enforces the desired timing and concurrency. As a result, our approach enables the creation of binary encoded portable concurrent time-accurate software components.}
}

@inproceedings{Engels2007a,
  author = {Gregor Engels AND Christian Soltenborn AND Heike Wehrheim},
  title = {Analysis of UML Activities Using Dynamic Meta Modeling},
  booktitle = {Proceedings of the conference on Formal Methods for Open Object-based Distributed Systems (FMOODS 2006), Oslo (Norway)},
  year = {2007},
  editor = {M. M. Bosangue, E. Broch Johnsen},
  pages = {76--90},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {June},
  abstract = {Dynamic Meta Modeling (DMM) is a universal approach to defining semantics for languages syntactically grounded on meta models. DMM has been designed with the aim of getting highly understandable yet precise semantic models which in particular allow for a formal analysis. In this paper, we exemplify this by showing how DMM can be used to give a semantics to and define an associated analysis technique for UML Activities.},
  series = {LNCS},
  volume = {4468}
}

@inproceedings{Bals07,
  author = {Jan-Christopher Bals AND Fabian Christ AND Gregor Engels AND Martin Erwig},
  title = {ClassSheets - model-based, object-oriented design of spreadsheet applications},
  booktitle = {Proceedings of the TOOLS Europe Conference (TOOLS 2007), Z{\"u}rich (Swiss)},
  year = {2007},
  pages = {383--398},
  publisher = {Journal of Object Technology},
  month = {October },
  abstract = {Using spreadsheets is the preferred method to calculate, display or store anything that fits into a table-like structure. They are often used by end users to create applications. But they have one critical drawback - they are very error-prone.To reduce the error-proneness, we purpose a new way of object-oriented modeling of spreadsheets prior to using them. These spreadsheet models, termed ClassSheets, are used to generate concrete spreadsheets on the instance level.By this approach sources of errors are reduced and spreadsheet applications are easier to understand. },
  journal = {Journal of Object Technology},
  volume = {6}
}

@inproceedings{Sauer2007,
  author = {Stefan Sauer AND Gregor Engels},
  title = {Easy Model-Driven Development of Multimedia User Interfaces with GuiBuilder},
  booktitle = {Proceeding of the 4th International Conference on Universal Access in Human-Computer Interaction (UAHCI, as Part of HCI International, 2007), Beijing (China)},
  year = {2007},
  editor = {C. Stephanidis},
  pages = {537--546},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  note = {Journal:Universal Access in HCI, Part IBook:HCI (5)},
  abstract = {GUI builder tools are widely used in practice to develop the user interface of software systems. Typically they are visual programming tools that support direct-manipulative assembling of the user interface components. We have developed the tool GuiBuilder which follows a model-driven approach to the development of graphical (multimedia) user interfaces. This allows a meta-design approach where user interface developers as well as prospective users of the system are supported in modelling the desired functionality of the GUI on a high level of abstraction that is easy to understand for all involved stakeholders. The model consists of compositional presentation diagrams to model the structure of the user interface and hierarchical statechart diagrams to model its behaviour. GuiBuilder then supports the transformation of the model to Java, i.e., the generation of a working user interface and the simulation of the modelled behaviour. Interactive sessions with the user interface can be recorded and replayed.},
  series = {LNCS},
  volume = {4554}
}

@inproceedings{Hess2007,
  author = {Andreas Hess AND Bernhard Humm AND Markus Vo{\ss} AND Gregor Engels},
  title = {Structuring Software Cities - A Multidimensional Approach},
  booktitle = {Proceedings of the 11th IEEE International Enterprise Distributed Object Computing Conference (EDOC 2007)},
  year = {2007},
  pages = {122--129},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  abstract = {Software cities alias application landscapes of large enterprises comprise tens or even hundreds of IT applications. Structuring software cities into domains is an important task of enterprise architects. The quality of the resulting domain model is crucial for the success of enterprise architecture management and an important tool for the governance of the development of an enterprise's application landscape. This paper presents a novel method for constructing domain models based on business services, business objects, and business dimensions. The method has been validated in numerous industrial projects. }
}

@inproceedings{Forster2007,
  author = {Alexander F{\"o}rster AND Gregor Engels AND Tim Schattkowsky AND Ragnhild Van Der Straeten},
  title = {Verification of Business Process Quality Constraints Based on Visual Process Patterns},
  booktitle = {Proceedings of the First Joint IEEE/IFIP Symposium on Theoretical Aspects of Software Engineering (TASE 2007), Shanghai (China)},
  year = {2007},
  pages = {197--208},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  abstract = {Business processes usually have to consider certain constraints like domain specific and quality requirements. The automated formal verification of these constraints is desirable, but requires the user to provide an unambiguous formal specification. In particular since the notations for business process modeling are usually visual flow-oriented languages, the notational gap to the languages usually employed for the formal specification of constraints, e.g., temporal logic, is significant and hard to bridge. Thus, our approach relies on UML Activities as a single language for the specification of both business processes and the corresponding constraints. For the expression of such constraints, we have provided a process pattern definition language based on specialized Activities. In this paper, we describe how model checking can be employed for formal verification of business processes against such patterns. For this, we present an automated transformation of the business process and the corresponding patterns into a transition system and temporal logic, respectively.}
}

@inproceedings{FoersterVLHCC06,
  author = {Alexander F{\"o}rster AND Tim Schattkowsky AND Gregor Engels AND Ragnhild Van Der Straeten},
  title = {A Pattern-driven Development Process for Quality Standard-conforming Business Process Models},
  booktitle = {IEEE Symposium on Visual Languages and Human-Centric Computing (VL/HCC 2006), Brighton (UK)},
  year = {2006},
  pages = {135--142},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  journal = {In Proc.}
}

@inproceedings{Engels2006d,
  author = {Gregor Engels AND Baris G{\"u}ldali AND Oliver Juwig AND Marc Lohmann AND Jan-Peter Richter},
  title = {Industrielle Fallstudie: Einsatz visueller Kontrakte in serviceorientierten Architekturen},
  booktitle = {Proceedings of the conference on Software Enginneering, Fachtagung des GI Fachbereichs Softwaretechnik (SE 2006), Leipzig (Germany)},
  year = {2006},
  editor = {B. Biel, M. Book, V. Gruhn},
  pages = {111--122},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {March},
  note = {Software Enginneering 2006, Fachtagung des GI Fachbereichs Softwaretechnik},
  abstract = {Serviceorientierte Architekturen (SOA) erlauben eine schnelle und kosteneffiziente Bereitstellung unterschiedlicher Funktionalit{\"a}ten zur Unterst{\"u}tzung der Gesch{\"a}ftsprozesse eines Unternehmens. Dazu werden fachliche Funktionalit{\"a}ten in Form von Enterprise Services zur Verf{\"u}gung gestellt. Die hohe Zahl von Enterprise Services erfordert eine geeignete semantische Beschreibung zu deren effizienten Verwaltung. Zur semantischen Beschreibung von Enterprise Services sowie zur Formulierung von Suchanfragen ist an der Universit{\"a}t Paderborn die Methode der visuellen Kontrakte entwickelt worden. Das Papier stellt die Ergebnisse der ersten Phase einer umfangreichen industriellen Fallstudie zur Evaluation der praktischen Anwendbarkeit visueller Kontrakte im Kontext einer SOA vor.},
  series = {Lecture Notes in Informatics},
  volume = {79}
}

@inproceedings{Engels2006f,
  author = {Gregor Engels AND Marc Lohmann AND Stefan Sauer AND Reiko Heckel},
  title = {Model-Driven Monitoring: An Application of Graph Transformation for Design by Contract},
  booktitle = {Proceedings of the 3rd International Conference on Graph Transformation (ICGT 2006), Natal (Brazil)},
  year = {2006},
  editor = {A. Corradini, H. Ehrig, U. Montanari, L. Ribeiro, G. Rozenberg},
  pages = {336--350},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {The model-driven development (MDD) approach for constructing software systems advocates a stepwise refinement and transformation process starting from high-level models to concrete program code. In contrast to numerous research efforts that try to generate executable function code from models, we propose a novel approach termed model-driven monitoring. Here, models are used to specify minimal requirements and are transformed into assertions on the code level for monitoring hand-coded programs during execution.We show how well-understood results from the graph transformation community can be deployed to support this model-driven monitoring approach. In particular, models in the form of visual contracts are defined by graph transitions with loose semantics, while the automatic transformation from models to JML assertions on the code level is defined by strict graph transformation rules. Both aspects are supported and realized by a dedicated Eclipse plug-in.},
  series = {LNCS},
  volume = {4178}
}

@inproceedings{Lohmann2006a,
  author = {Marc Lohmann AND Gregor Engels AND Stefan Sauer},
  title = {Model-driven Monitoring: Generating Assertions from Visual Contracts},
  booktitle = {Proceedings of the 21st IEEE International Conference on Automated Software Engineering (ASE 06), Tokyo (Japan)},
  year = {2006},
  pages = {355--356},
  publisher = {IEEE Computer Society},
  address = {Los Alamitos, CA, USA},
  abstract = {The Visual Contract Workbench is a tool that supports model-driven development of software systems by lifting the Design by Contract idea, which is usually used at the code level, to the model level. It uses visual contracts for graphically specifying the pre- and post-conditions of an operation. Java classes with JML (Java Modeling Language) assertions are generated from visual contracts to facilitate automatic monitoring of the correctness of the programmer's implementation.}
}

@inproceedings{Engels2006e,
  author = {Gregor Engels AND Jan Hendrik Hausmann AND Marc Lohmann AND Stefan Sauer},
  title = {Teaching UML Is Teaching Software Engineering Is Teaching Abstraction},
  booktitle = {Proceedings of the Satellite Events at the MoDELS 2005 Conference, Montego Bay (Jamaica)},
  year = {2006},
  editor = {J.-M. Bruel},
  pages = {306--319},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  note = {Proceedings of the workshopt on Satellite Events at the MoDELS 2005 Conference (MoDELS 2005 International Workshops OCLWS, MoDeVA, MARTES, AOM, MTiP, WiSME, MODAUI, NfC, MDD, WUsCAM, Montego Bay, Jamaica)},
  abstract = {As the Unified Modeling Language (UML) has by now seen widespread and successful use in the software industry and academia alike, it has also found its way into many computer science curricula. An outstanding advantage of teaching UML is that it enables an illustration of many crucial concepts of software engineering, far beyond its concrete notation. Most important among these concepts is that of abstraction. We present a course design which demonstrates the use of UML as a vehicle for teaching such core concepts of software engineering. Multimedia elements and tools help to efficiently convey the courses message to the students.},
  series = {LNCS},
  volume = {3844 / 2006}
}

@inproceedings{Schattkowsky2006c,
  author = {Tim Schattkowsky AND Jan Hendrik Hausmann AND Gregor Engels},
  title = {Using UML Activities for System-on-Chip Design and Synthesis},
  booktitle = {Proceedings of the International Conference on Model Driven Engineering Languages and Systems (MoDELS 2006), Genova (Italy)},
  year = {2006},
  editor = {O. Nierstrasz, J. Whittle, D. Harel, G. Reggio},
  pages = {737--752},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {The continuous advances in manufacturing Integrated Circuits (ICs) enable complete systems on a single chip. However, the design effort for such System-on-Chip (SoC) solutions is significant. The productivity of the design teams currently lags behind the advances in manufacturing and this design productivity gap is still widening. One important reason is the lack of abstraction in traditional Hardware Description Languages (HDLs) like VHDL. The UML provides more abstract concepts for modeling behavior that can also be employed for hardware design. In particular, the new UML Activity semantics fit nicely with the inherent data flow in hardware systems. Therefore, we introduce a UML-based design approach for complete SoC specification. Our approach enables generation of complete synthesizable HDL code. The equivalent hardware can be automatically generated using the existing tools chains. As an example, we outline Handel-C code generation for an MP3 decoder design.},
  series = {LNCS},
  volume = {4199/2006}
}

@inproceedings{Foerster2005,
  author = {Alexander F{\"o}rster AND Gregor Engels AND Tim Schattkowsky},
  title = {Activity Diagram Patterns for Modeling Quality Constraints in Business Processes},
  booktitle = {Proceedings of the 8th International Conference on Model Driven Engineering Languages and Systems (MoDELS 2005), Montego Bay (Jamaica)},
  year = {2005},
  editor = {L. C. Briand, C. Williams},
  pages = {2--16},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  series = {LNCS},
  volume = {3713}
}

@inproceedings{Guo2005,
  author = {Ping Guo AND Gregor Engels AND Reiko Heckel},
  title = {Architectural Style - Based Modeling and Simulation of Complex Software Systems},
  booktitle = {Proceedings of the 12th Asia-Pacific Software Engineering Conference (APSEC 2005), Taipei (Taiwan)},
  year = {2005},
  pages = {367--374},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  month = {December},
  abstract = {The design and development of complex software systems is a difficult task, and it is not easy to ensure the quality of a developed software. The paper presents an architectural style-based approach to specifying and analyzing complex software systems. The approach is developed based on UML-like meta models and graph transformation techniques to support sound methodological principals, formal analysis and refinement. The approach is illustrated through the specification and simulation of architectural styles of mobile computing middleware, where three abstract levels of architectural styles are defined in order to decrease the complexity brought by mobility.}
}

@inproceedings{Engels2005d,
  author = {Gregor Engels AND Martin Erwig},
  title = {ClassSheets: automatic generation of spreadsheet applications from object-oriented specifications},
  booktitle = {Proceedings of the 20th IEEE/ACM International Conference on Automated Software Engineering (ASE 2005), Long Beach, CA (USA)},
  year = {2005},
  pages = {124--133},
  publisher = {ACM Press},
  address = {New York, NY, USA},
  month = {November},
  abstract = {Spreadsheets are widely used in all kinds of business applications.Numerous studies have shown that they contain manyerrors that sometimes have dramatic impacts. One reasonfor this situation is the low-level, cell-oriented developmentprocess of spreadsheets.We improve this process by introducing and formalizinga higher-level object-oriented model termed ClassSheet.While still following the tabular look-and-feel of spreadsheets,ClassSheets allow the developer to express explicitlybusiness object structures within a spreadsheet, whichis achieved by integrating concepts from the UML (UnifiedModeling Language). A stepwise automatic transformationprocess generates a spreadsheet application that is consistentwith the ClassSheet model. Thus, by deploying theformal underpinning of ClassSheets, a large variety of errorscan be prevented that occur in many existing spreadsheetapplications today.The presented ClassSheet approach links spreadsheet applicationsto the object-oriented modeling world and advocatesan automatic model-driven development process forspreadsheet applications of high quality.}
}

@inproceedings{Lohmann2005,
  author = {Marc Lohmann AND Stefan Sauer AND Gregor Engels},
  title = {Executable Visual Contracts},
  booktitle = {Proceedings of the IEEE Symposium on Visual Languages and Human-Centric Computing (VL/HCC 2005)},
  year = {2005},
  editor = {M. Erwig, A. Sch{\"u}rr},
  pages = {63--70},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  abstract = {Design by Contract (DbC) is widely acknowledged to be a powerful technique for creating reliable software. DbC allows developers to specify the behavior of an operation precisely by pre- and post-conditions. Existing DbC approaches predominantly use textual representations of contracts to annotate the actual program code with assertions. In the Unified Modeling Language (UML), the textual Object Constraint Languages (OCL) supports the specification of pre- arid post-conditions by constraining the model elements that occur in UML diagrams. However; textual specifications in OCL can become complex and cumbersome, especially for software developers who are typically not used to OCL. In this paper, we propose to specify the pre- and post-conditions of an operation visually by a pair of UML object diagrams (visual Contract). We define a mapping of visual contracts into Java classes that are annotated with behavioral interface specifications in the Java Modeling Language (JML). The mapping supports testing the correctness of the implementation against the specification using JML tools, which include a runtime assertion checker. Thus we make the visual contracts executable.}
}

@inproceedings{Engels04,
  author = {Gregor Engels AND Stefan Sauer},
  title = {Guest Editors' Introduction},
  booktitle = {International Journal of Software Engineering and Knowledge Engineering (IJSEKE)},
  year = {2004},
  editor = {G. Engels, S. Sauer},
  pages = {543--544},
  publisher = {World Scientific Publishing},
  month = {December},
  volume = {14}
}

@inproceedings{Kuster2003,
  author = {Jochen K{\"u}ster AND Gregor Engels},
  title = {Consistency Management within Model-Based Object-Oriented Development of Components},
  booktitle = {Proceedings of the conference on Formal Methods for Components and Objects (FMCO 2003), Leiden (Netherlands)},
  year = {2003},
  editor = {F. S. de Boer and M. M. Bonsangue and S. Graf and W. P. de Roever},
  pages = {157-176},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  abstract = {The Unified Modeling Language (UML) favors the construction of models composed of several submodels, modeling the system components under development at different levels of abstraction and from different viewpoints. Currently, consistency of object-oriented models expressed in the UML is not defined in the UML language specification. This allows the construction of inconsistent UML models. Defining consistency of UML models is complicated by the fact that UML models are applied differently, depending on the application domain and development process. As a consequence, a form of consistency management is required that allows the software engineer to define, establish and manage consistency, tailored specifically to the development context. In recent years, we have developed a general methodology and tool support to overcome this problem. The methodology is based on a thorough study of the notion of consistency and has led to a generic definition of the notion of consistency. Our methodology itself aims at a step-wise systematic construction of a consistency management process, by providing a number of activities to be performed by the software engineer. It is complemented by a tool called Consistency Workbench which supports the software engineer in performing the methodology. In this paper, we provide an overview and summary of our approach.},
  series = {LNCS},
  volume = {3188}
}

@inproceedings{KusterHE03,
  author = {Jochen K{\"u}ster AND Reiko Heckel AND Gregor Engels},
  title = {Defining and Validating Transformations of UML Models},
  booktitle = {Proceedings of the conference on Human Centric Computing Languages and Environments (HCC 2003), Auckland (New Zealand)},
  year = {2003},
  pages = {145--152},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  abstract = {With the success of the UML, the ability of transforming models into programs or formal specifications becomes a key to automated code generation or verification in the software development process. In this paper, we describe a concept for specifying model transformations by means of graph transformation rules on the UML meta model. In order to validate the termination and uniqueness of such transformations, we derive a number of sufficient criteria from basic results of the theory of graph transformation. This ensures that the rules can be executed automatically while, at the same time, providing a high-level visual model of the transformation.}
}

@inproceedings{Engels2003d,
  author = {Gregor Engels AND Stefan Sauer AND Bettina Neu},
  title = {Integrating software engineering and user-centred design for multimedia software developments},
  booktitle = {Proceedings of the conference on Human-Centric Computing Languages and Environments (HCC 2003), Auckland (New Zealand)},
  year = {2003},
  pages = {254--256},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  month = {October },
  abstract = {The object-oriented modeling of interactive multimedia applications in the OMMMA approach is designed to enable multimedia software developers to create comprehensive analysis and design models of multimedia software. For development of highly usable multimedia applications, this approach must be embedded in a more holistic development process that takes a user-oriented perspective on multimedia software development. In this paper, we elaborate on the differences between usercentred design activities and object-oriented software design activities and outline their integration in a comprehensive development process.}
}

@inproceedings{Engels2003c,
  author = {Gregor Engels AND Jochen K{\"u}ster AND Reiko Heckel AND Marc Lohmann},
  title = {Model Based Verification and Validation of Properties},
  booktitle = {Proceedings of the conference on Uniform Approaches to Graphical Process Specification Techniques (UNIGRA 2003, Satellite Event of the ETAPS 2003), Warsaw (Poland)},
  year = {2003},
  editor = {R. Bardohl, H. Ehrig},
  pages = {1--18},
  publisher = {Elsevier},
  month = {June},
  abstract = {One of the key issues in software development, like in all engineering problems, is to ensure that the product delivered meets its specification. Verification and validation are well-established techniques for ensuring the quality of a product within the overall software development lifecycle. With models being expressed in the Unified Modeling Language, the application of verification and validation is complicated. Firstly, concerning verification, a UML model is typically not the input language of a verification tool. Secondly, with regards to validation, a UML model is also not directly executable. In this paper, we show how verification and validation can be achieved for UML models. Within our approach, graph transformation techniques are applied for automated translation of UML models into a language understood by a verification tool or directly into an implementation. By the use of such semantic-preserving transformations, both verification and validation can be lifted up to the model level, allowing for a seamless integration of verification and validation into a UML-based development process.},
  series = {Electronic Notes in Theoretical Computer Science},
  volume = {82}
}

@inproceedings{Alfert2003,
  author = {Klaus Alfert AND Ernst-Erich Doberkat AND Gregor Engels AND Marc Lohmann AND Johannes Magenheim AND Andy Sch{\"u}rr},
  title = {MuSofT: Multimedia in der Softwaretechnik},
  booktitle = {Proceedings of the conference on Software Engineering im Unterricht der Hochschulen (SEUH 2003), Berlin (Germany)},
  year = {2003},
  editor = {J. Siedersleben, D. Weber-Wulff},
  pages = {70--80},
  publisher = {dpunkt Verlag},
  address = {Heidelberg},
  month = {February},
  note = {SEUH 8 - Software Engineering im Unterricht der Hochschulen, Berlin 2003},
  abstract = {Im BMBF-Verbundprojekt MuSofT werden multimediale Lehrmaterialien f{\"u}r die Lehre der Softwaretechnik entwickelt. In diesem Papier stellen wir die Bem{\"u}hungen innerhalb von MuSofT vor, eine qualitativ hochwertige und nachhaltige Entwicklung von Lernobjekten zu realisieren. Wir legen den Fo-kus dabei auf die didaktischen Grundannahmen, die inhaltliche und stilisti-sche Abstimmung zwischen den Materialien sowie die gleichf{\"o}rmige Be-schreibung der Materialien durch Metadaten, die eine effektive Recherche des Materials innerhalb des MuSofT-Portals erm{\"o}glichen.}
}

@inproceedings{Engels03,
  author = {Gregor Engels AND Klaus Alfert AND Ernst-Erich Doberkat},
  title = {MuSofT: Multimedia in der SoftwareTechnik},
  booktitle = {Proceeding of the 1. e-Learning Fachtagung Informatik (DeLFI 2003), Garching bei M{\"u}nchen (Germany)},
  year = {2003},
  editor = {A. Bode, J. Desel, S. Ratmayer, M. Wessner},
  pages = {115-119},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {September },
  series = {Lecture Notes in Informatics},
  volume = {37}
}

@inproceedings{Engels2003b,
  author = {Gregor Engels AND Reiko Heckel AND Jochen K{\"u}ster},
  title = {The Consistency Workbench: A Tool for Consistency Management in UML-based Development},
  booktitle = {Proceedings of the 6th International Conference on The Unified Modeling Language: Modeling Languages and Applications (UML 2003), San Francisco, CA (USA)},
  year = {2003},
  editor = {P. Stevens, J. Whittle, G. Booch},
  pages = {356--359},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {With the Unified Modeling Language becoming applied indiverse contexts, the ability of defining and checking customized consistencyconditions is gaining increasing importance. In this paper, weintroduce the Consistency Workbench for defining and establishing consistencyin a UML-based development process.},
  series = {LNCS},
  volume = {2863}
}

@inproceedings{Engels02a,
  author = {Gregor Engels AND Reiko Heckel AND Jochen K{\"u}ster AND Luuk Groenewegen},
  title = {Consistency-Preserving Model Evolution through Transformations},
  booktitle = {Proceedings of the 5th International Conference on The Unified Modeling Language (UML 2002), Dresden (Germany)},
  year = {2002},
  editor = {J.-M. J{'e}z{'e}quel, H. Hussmann, S. Cook},
  pages = {212--226},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {Oktober},
  series = {LNCS},
  volume = {2460}
}

@inproceedings{Engels2002e,
  author = {Gregor Engels AND Jochen K{\"u}ster AND Luuk Groenewegen},
  title = {Consistent Interaction Of Software Components},
  booktitle = {Proceedings of the conference on Integrated Design and Process Technology (IDPT 2002), Pasadena, CA (USA)},
  year = {2002},
  pages = {2--22},
  publisher = {IOS Press},
  month = {June },
  abstract = {Constructing complex software systems by integrating different software components is a promising and challenging approach. With the functionality of software components given by models it is possible to ensure consistency of such models before implementation in order to successfully build the system. Models consisting of different submodels, the absence of an overall formal semantics and the numerous possibilities of employing models requires the development of techniques ensuring the consistency. In this paper, we discuss the issue of consistency of models made up of different submodels proposing a concept for the management of consistency. Consistency management relies on a consistency concept and a process for ensuring consistency of models. We introduce a consistency concept for software components modeled in the Unified Modeling Language (UML) and devise suitable consistency checks. On this basis, we propose a process how to locate and resolve inconsistencies, thus ensuring the consistency of models and by that the consistency of component-based systems derived from those models.},
  journal = {Journal of Integrated Design \& Process Science},
  volume = {6}
}

@inproceedings{Depke2002,
  author = {Ralph Depke AND Gregor Engels AND Matthew Langham AND Bj{\"o}rn L{\"u}tkemeier AND Sebastian Th{\"o}ne},
  title = {Process-Oriented, Consistent Integration of Software Components},
  booktitle = {Proceedings of the conference on Prolonging Software Life: Development and Redevelopment (COMPSAC 2002), Oxford (England)},
  year = {2002},
  pages = {13--18},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  month = {August},
  note = {COMPSAC '02: Proceedings of the 26th International Computer Software and Applications Conference on Prolonging Software Life: Development and Redevelopment},
  abstract = {The integration of software components becomes a more and more important issue in software engineering. Process-oriented approaches should provide automated information processes. Therefore, the software components have to be integrated in a consistent way, i.e., their export interfaces have to be respected by the importing components. Furthermore, the type system of component interfaces has to support a tunable degree of freedom. This allows the insertion of components with interfaces of restricted but sufficient degree of compatibility. In this paper, we develop a concept for consistent and flexible integration of components. We present a process modeling language that combines UML and XML in order to support consistent, flexible, and executable processes. Finally, we provide a formalization of the proposed component type system.}
}

@inproceedings{Engels2002f,
  author = {Gregor Engels AND Jan Hendrik Hausmann AND Reiko Heckel AND Stefan Sauer},
  title = {Testing the Consistency of Dynamic UML Diagrams},
  booktitle = {Proceedings of the Sixth International Conference on Integrated Design and Process Technology (IDPT 2002), Pasadena, CA (USA)},
  year = {2002},
  month = {June},
  note = {Pasadena, CA, USA}
}

@inproceedings{EngelsKGH2001b,
  author = {Gregor Engels AND Jochen K{\"u}ster AND Luuk Groenewegen AND Reiko Heckel},
  title = {A methodology for specifying and analyzing consistency of object-oriented behavioral models},
  booktitle = {Proceedings of the 8th European Software Engineering Conference (ESEC 2001) and 9th ACM SIGSOFT Symposium on the Foundations of Software Engineering (FSE-9), Vienna (Austria)},
  year = {2001},
  editor = {V. Gruhn},
  pages = {186--195},
  publisher = {ACM Press},
  address = {New York, NY, USA},
  month = {September },
  abstract = {Object-oriented modeling favors the modeling of object behavior from different viewpoints and the successive refinement of behavioral models in the development process. This gives rise to consistency problems of behavioral models. The absence of a formal semantics for UML models and the numerous possibilities of employing behavioral models within the development process lead to the rise of a number of different consistency notions. In this paper, w e discuss the issue of consistency of behavioral models in the UML and present a general methodology how consistency problems can be dealt with. According to the methodology, those aspects of the models relevant to the consistency are mapped to a semantic domain in which precise consistency tests can be formulated. The choice of the semantic domain and the definition of consistency conditions can be used to construct different consistency notions. We show the applicability of our methodology by giving an example of a concrete consistency problem of concurrent object-oriented models.},
  volume = {26}
}

@inproceedings{HE01,
  author = {Reiko Heckel AND Gregor Engels},
  title = {Graph Transformation as a Meta Language for Dynamic Modeling and Model Evolution},
  booktitle = {Proceeding of International Special Session on Formal Foundations of Software Evolution (FFSE 2001, co-located with the Conference on Software Maintenance and Reengineering), Lisbon (Portugal)},
  year = {2001},
  editor = {T. Mens, M. Wermelinger},
  pages = {42-47},
  publisher = {Universidade Nova de Lisboa},
  address = {Lisbon}
}

@inproceedings{Engels2001a,
  author = {Gregor Engels AND Reiko Heckel AND Jochen K{\"u}ster},
  title = {Rule-Based Specification of Behavioral Consistency Based on the UML Meta-model},
  booktitle = {Proceedings of the conference on The Unified Modeling Language, Modeling Languages, Concepts, and Tools (UML 2001), Toronto (Canada)},
  year = {2001},
  editor = {M. Gogolla, C. Kobryn},
  pages = {272--287},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  abstract = {Object-oriented modeling favors the modeling of object behavior from different viewpoints and at different levels of abstraction. This gives rise to consistency problems between overlapping or semantically related submodels.The absence of a formal semantics for the UML and the numerous ways of employing the language within the development process lead to a number of different consistency notions. Therefore, general meta-level techniques are required for specifying, analyzing, and communicating consistency constraints. In this paper, we discuss theissue of consistency of behavioral models in the UML and present techniques for specifying and analyzing consistency. Using meta-model rules we transform elements of UML models into a semantic domain. Then, consistency constraints can by specified and validated using the language and the tools of the semantic domain. This general methodology is exemplified by the problem of protocol statechart inheritance.},
  volume = {2185}
}

@inproceedings{Sauer2001,
  author = {Stefan Sauer AND Gregor Engels},
  title = {UML-based Behavior Specification of Interactive Multimedia Applications},
  booktitle = {Proceedings of the IEEE Symposia on Human Centric Computing Languages and Environments (HCC 2001), Stresa (Italy)},
  year = {2001},
  pages = {248--255},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  month = {September},
  note = {Best Paper of HCC 2001.},
  abstract = {Availability of precise, yet usable modeling languages is essential to the construction of multimedia systems based on software engineering principles and methods. Although several languages have been proposed for the specification of isolated multimedia system aspects, there not yet exists an integrated modeling language that adequately supports multimedia software development in practice. We propose an extension of the Unified Modeling Language (UML) for the integrated specification of multimedia systems based on an object-oriented development method. Since integration of co-existing timed procedural and interactive behavior is at the heart of multimedia systems, we focus on UML-based specification of behavior in this paper. In addition, we outline how these behavioral aspects are to be integrated with media, presentation, and software architecture modeling to achieve a coherent and consistent model.}
}

@inproceedings{Hausmann2000,
  author = {Gregor Engels AND Jan Hendrik Hausmann AND Reiko Heckel AND Stefan Sauer},
  title = {Dynamic Meta-Modeling: A Graphical Approach to the Operational Semantics of Behavioral Diagrams in UML},
  booktitle = {Proceedings of the 3rd international conference on the Unified Modeling Language (UML 2000), York (UK)},
  year = {2000},
  editor = {A. Evans, S. Kent, B. Selic},
  pages = {323--337},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  note = {Third International Conference},
  abstract = {In this paper, dynamic meta modeling is proposed as a new approach to the operational semantics of behavioral UML diagrams. The dynamic meta model extends the well-known static meta model by a speci.cation of the system's dynamics by means of collaboration diagrams. In this way, it is possible to de.ne the behavior of UML diagrams within UML.The conceptual idea is inherited from Plotkin's structured operational semantics (SOS) paradigm, a style of semantics speci.cation for concurrent programming languages and process calculi: Collaboration diagrams are used as deduction rules to specify a goal-oriented interpreter for the language. The approach is exemplified using a fragment of UML statechart and object diagrams.Formally, collaboration diagrams are interpreted as graph transformation rules. In this way, dynamic UML semantics can be both mathematically rigorous so as to enable formal specifications and proofs and, due to the use of UML notation, understandable without prior knowledge of heavy mathematic machinery. Thus, it can be used as a reference by tool developers, teachers, and advanced users.},
  series = {LNCS},
  volume = {1939}
}

@inproceedings{Engels01,
  author = {Gregor Engels AND Reiko Heckel},
  title = {Graph Transformation as a Conceptual and Formal Framework for System Modeling and Model Evolution},
  booktitle = {Proceedings of the 27th International Colloquium on Automata, Languages and Programming (ICALP 2000), Geneva (Switzerland)},
  year = {2000},
  pages = {127-150},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {July},
  series = {LNCS},
  volume = {1853}
}

@inproceedings{Engels2000e,
  author = {Gregor Engels AND Luuk Groenewegen},
  title = {Object-Oriented Modeling - A Roadmap},
  booktitle = {Proceedings of the Conference on The Future of Software Engineering - Special Track at 22nd International Conference on Software Engineering (ICSE 2000), Limerick (Ireland)},
  year = {2000},
  editor = {A. Finkelstein},
  pages = {103--116},
  publisher = {ACM Press},
  address = {New York, NY, USA},
  month = {June },
  abstract = {Object-oriented modeling has become the de-facto standard in the early phases of a software development process during the last decade. The current state-of-the-art is dominated by the existence of the Unified Modeling Language (UML), the development of which has been initiated and pushed by industry.This paper presents a list of requirements for an ideal object-oriented modeling language and compares it with the achievements of UML and other object-oriented modeling approaches. This forms the base for the discussion of a roadmap for object-oriented modeling, which is structured according to a classification scheme of six different themes, which are language-, model- orprocess-related, respectively.}
}

@inproceedings{Engels2000c,
  author = {Gregor Engels AND Reiko Heckel AND Stefan Sauer},
  title = {UML - A Universal Modeling Language?},
  booktitle = {Proceedings of the 21st International Conference on Application and Theory of Petri Nets (ICATPN 2000), Aarhus (Denmark)},
  year = {2000},
  editor = {M. Nielsen, D. Simpson},
  pages = {24--38},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {June},
  abstract = {Abstract. The Unified Modeling Language (UML) is the de facto industrial standard of an object-oriented modeling language. It consists of several sublanguages which are suited to model structural and behavioral aspects of a software system. The UML was developed as a general-purpose language together with intrinsic features to extend the UML towards problem domain-specific profiles. The paper illustrates the language features of the UML and its adaptation mechanisms. As a conclusion, we show that the UML or an appropriate, to be defined core UML, respectively, may serve as a universal base of an object-oriented modeling language. But this core has to be adapted according to problem domain-specific requirements to yield an expressive and intuitive modeling language for a certain problem domain.},
  series = {LNCS},
  volume = {1825}
}

@inproceedings{Sauer1999a,
  author = {Stefan Sauer AND Gregor Engels},
  title = {Extending UML for Modeling of Multimedia Applications},
  booktitle = {Proceedings of the IEEE Symposium on Visual Languages (VL 1999), Tokyo (Japan)},
  year = {1999},
  editor = {M. Hirakawa, P. Mussio},
  pages = {80--87},
  publisher = {IEEE Computer Society},
  address = {Tokyo, Japan},
  note = {Awarded at the VL/HCC 2010 as the most influential VL/HCC paper of the last decade.},
  abstract = {An analysis of how visual modeling of structure and dynamic behavior of a multimedia application differs from modeling conventional software yields that aspects of the graphical user interface and time-dynamic behavior ought to be integral parts of a coherent multimedia application model. In this sense, we extend the model-view-controller paradigm towards multimedia.As a result, we present OMMMA-L, a visual Language for the Object-Oriented Modeling of MultiMedia Applications that is based on the Unified Modeling Language (UML). The structural and behavioral diagram types of UML have been analyzed and are adapted and extended according to multimedia application characteristics.A presentation diagram is introduced and integrated to adequately describe the visual presentation. In addition to explaining the different diagram types, we also give pragmatic guidelines on how to deploy and combine the various diagrams.}
}

@inproceedings{Engels1999c,
  author = {Gregor Engels AND Ralph Depke AND Christoph Borowski},
  title = {Konzeption und objektorientierte Realisierung einer internet-basierten Datenbankanwendung},
  booktitle = {Kolloquium Software-Entwicklung - Methoden, Werkzeuge, Erfahrungen},
  year = {1999},
  editor = {H. J. Scheibl},
  pages = {531--540},
  publisher = {Technische Akademie Esslingen},
  address = {Ostfildern},
  month = {September},
  abstract = {Today e-commerce applications use web browsers as an uniform user interface and they rely on databases as datasources. Different technologies exist for database access: common gateway interface (CGI), Java and its databaseinterface java database connectivity (JDBC), proprietary approaches of database vendors, etc. We present criteria forthe selection of an appropriate solution and we successivly apply them in our application development process.Throughout the development process of internet based database applications object oriented techniques can be used.The unified modeling language (UML) is used for requirement analysis and design of the application and theimplementation proceeds with the programming language Java. The transition from the object oriented modelinglanguage UML to the object oriented programming language Java succeeds smoothly. We report on our experience withthe modeling tool Rational Rose 98 of Rational, Inc. We use Java and JDBC to implement a seminar reservation systemthat can be regarded as a small e-commerce application.},
  volume = {8}
}

@inproceedings{EngelsHSW1999,
  author = {Gregor Engels AND Roland H{\"u}cking AND Stefan Sauer AND Annika Wagner},
  title = {UML Collaboration Diagrams and Their Transformation to Java},
  booktitle = {Proceddings of The Unified Modeling Language: Beyond the Standard, Second International Conference (UML 99), Fort Collins, Colorado, USA},
  year = {1999},
  editor = {R. France, B. Rumpe},
  pages = {473--488},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  series = {LNCS},
  volume = {1723}
}

@inproceedings{Depke1998,
  author = {Ralph Depke AND Gregor Engels AND Katharina Mehner AND Stefan Sauer AND Annika Wagner},
  title = {Ein Ansatz zur Verbesserung des Entwicklungsprozesses von Multimedia-Anwendungen},
  booktitle = {Proceedings of the GI-Fachtagung on Softwaretechnik (1998), Paderborn (Germany)},
  year = {1998},
  pages = {12--19},
  publisher = {GI},
  month = {September },
  journal = {Softwaretechnik-Trends},
  volume = {18}
}

@inproceedings{Engels97,
  author = {Gregor Engels AND Reiko Heckel AND Gabriele Taentzer AND Hartmut Ehrig},
  title = {A View-Oriented Approach to System Modelling Using Graph Transformations},
  booktitle = {Proceedings European Software Engineering Conference (ESEC 1997), Z{\"u}rich (Switzerland)},
  year = {1997},
  editor = {M. Jazayeri, H. Schauer},
  pages = {327--343},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {The idea of a combined reference model- and view-based specification approach has been proposed recently in the software engineering community. In this paper we present a specification technique based on graph transformations which supports such a development approach. The use of graphs and graph transformations supports an intuitive understanding and an integration of static and dynamic aspects on a well-defined semantical base. On this background, formal notions of view and view relation are developed and the behaviour of views is described by a loose semantics. We define a construction for automatic view integration which assumes that the dependencies between different views are described by a reference model. The views and the reference model are kept consistent manually, which is the task of a model manager. All concepts and results are illustrated at the well-known example of a banking system.},
  volume = {1301}
}

@inproceedings{EEH+96,
  author = {Gregor Engels AND Hartmut Ehrig AND Reiko Heckel AND Gabriele Taentzer AND Andrea Corradini},
  title = {A View-Based Approach to System Modelling},
  booktitle = {Report on Dagstuhl-Seminar 9637 on Graph Transformations in Computer Science},
  year = {1996},
  editor = {H. Ehrig, U. Montanari, G. Rozenberg, H.-J. Schneider},
  pages = {11},
  publisher = {Technical University of Berlin},
  month = {September},
  abstract = {In order to manage the complexity of large system specifications, they have to be decomposed into subspecifications. Each subspecification describes a certain part of the system. This might be a certain aspect, like the data, dynamic, or functional aspect, as it is known from object-oriented modelling techniques. Or it might be a certain view onto the system, as it is known from database modelling techniques. The talk motivates the usage of views in graph grammarbased specifications. First, the usage of typed graph grammars inherently ensures an integration of the data and the functional aspect within a view. Second, it is explained that it is not appropriate in case of views to have a fixed semantics.The standard fixed semantics, i.e. a graph transformation system, has to be relaxed to a loose semantics, i.e. a graph transition system. This reflects the idea that a view models only a part of the complete system. Other views may overlap a view with respect to data or functionality. A complete system specification is yielded by exploiting the approach of cooperative parallel composition of graph grammars (see talk by Leila Ribeiro).},
  series = {Dagstuhl-Seminar-Report},
  volume = {155}
}

@inproceedings{Bunje1996,
  author = {Tineke de Bunje AND Gregor Engels AND Luuk Groenewegen AND Aart Matsinger AND Martin Rijnbeek},
  title = {Industrial maintenance modelled in SOCCA: an experience report},
  booktitle = {Proceedings of the Fourth International Conference on the Software Process (ICSP 1996), Brighton (UK)},
  year = {1996},
  pages = {13--26},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  abstract = {A large industrial process, software maintenance, has been modelled by using the process modelling language SOCCA. The paper reports about the experiences with this trial. In particular, feasibility, expressiveness, quality and the overall benefits of a formal SOCCA model are discussed and compared to the formerly existing informal process description. In order to illustrate the results, a well chosen process model fragment from the larger model is outlined in detail. It addresses in particular the human-intensive cooperation within the process and shows the seamless combination of technical components and human agent components in the SOCCA model. The main conclusions from this trial are that formal SOCCA models are suited to model realistic industrial processes and that due to an intrinsic modular structure of a SOCCA model, even huge models remain reasonably readable and understandable}
}

@inproceedings{EngelsGK1996a,
  author = {Gregor Engels AND Luuk Groenewegen AND Gerti Kappel},
  title = {Object-oriented specification of coordinated collaboration},
  booktitle = {Proceedings of IFIP World Conference on IT Tools (1996), Canberra (Australia)},
  year = {1996},
  editor = {N. Terashima, Ed. Altman},
  pages = {437--452},
  publisher = {Chapman \& Hall},
  month = {September },
  abstract = {Object-oriented specification mechanisms have become famous for modelling structure and behaviour together in terms of autonomous objects communicating via message passing. However, whereas most object-oriented specification methods are strong in modelling the local behaviour of single objects, they fall short on modelling the coordinated behaviour and collaboration of several objects together The aim of this paper is to contribute to fill this gap. The paper reports on concepts, language constructs, and experiences with three collaboration formalisms in the area of object-oriented specifications.}
}

@inproceedings{Ehrig1996a,
  author = {Hartmut Ehrig AND Reiko Heckel AND Julia Padberg AND Gabriele Taentzer AND Uwe Wolter AND Andrea Corradini AND Gregor Engels},
  title = {Synchronization of Views and Loose Semantics of Typed Graph Productions},
  booktitle = {Report on the Dagstuhl-Seminar 9637 on Graph Transformations in Computer Science},
  year = {1996},
  pages = {11--12},
  publisher = {Technical University of Berlin},
  month = {September},
  abstract = {The concept of views is used on two levels. First, so-called design views are developed for structuring specifications, that is, a system is modeled according to different views (e.g., representing the needs of different kinds of users) which have to be synchronized afterwards in order to build the whole system. Views can be specified by means of typed graph transformation systems, where the type graph determines the visible types and the productions describe the known operations of that view. The synchronization of views is done by the construction of cooperative parallel composition of graph transformation systems, developed by Leila Ribeiro and presented at the same seminar.If the specification is complete, a view may describe an observation of the system in operation. In this case we speak of a user view. It turns out that the semantics of such a view cannot be described by computations (i.e., graph transformations), but just by observations of computations of the global system. Such observations of computations cannot be represented by graph transformations in the usual sense because a local view may lack operations (productions) of the global system, so that state changes may be observed that do not have a cause in the local view.Therefore, the notion of graph transition is introduced as loose semantics for productions, where the production specifies only a lower bound to the activities that are to happen during application. Contrastingly, in the classical doublepushout approach to graph rewriting, productions are interpreted as complete descriptions of the transformations to be performed.For typed graph transformation systems a transition sequence semantics is developed, comprising all finite and infinite sequences of transitions in a system.Moreover, this semantics is shown to be compositional w.r.t. the synchronization of views.}
}

@inproceedings{Engels1994b,
  author = {Gregor Engels AND Gerti Kappel},
  title = {Object-Oriented System Development: Will the New Approach Solve Old Problems?},
  booktitle = {Proceedings of the IFIP 13th World Computer Congress on Information Processing, Hamburg (Germany)},
  year = {1994},
  editor = {K. Duncan and K. Krueger},
  pages = {434--441},
  publisher = {Elsevier},
  month = {August },
  abstract = {Object-oriented system development is wideley recognized as improving productivity and reducing system maintenance costs. However, existing approaches have not sufficiently addressed the following three questions which are equally important to users and researchers. Firstly, what are the benefits of object-oriented system development compared to traditional approaches? Secondly, what are the essential features of an objectoriented life cycle model to fulfill the benefits of object-oriented development? And thirdly, what are the pitfalls of object-oriented development and how to cope with them? The paper investigates answers to all three questions in concert.},
  volume = {3}
}

@inproceedings{Ebert1994a,
  author = {J{\"u}rgen Ebert AND Gregor Engels},
  title = {Structural and Behavioural Views on OMT-Classes},
  booktitle = {Proceedings of the International Symposium on Object-Oriented Methodologies and Systems (ISOOMS 1994), Palermo (Italy)},
  year = {1994},
  editor = {E. Bertino, S. Urban},
  pages = {142-157},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Object-oriented specification languages provide means to specify the static structure, as well as the allowed dynamic behaviour of objects. Here, the dynamic behaviour is usually described by giving the methods and a state transition diagram which defines the allowed sequences of methods on objects of a certain class.Specialized classes are defined using the inheritance relationship. In order to enable reusability while guaranteeing type substitutability, subclass specifications have to be compatible with respect to static and dynamic aspects with their corresponding superclass specifications.Classes have to provide a large shopping list of operations to satisfy the needs of all possible users. The interests of specific users are often restricted to a subset of operations and thus to a restricted behaviour.This paper describes a formalization of class descriptions given by attributes, operations, as well as state transition diagrams. It defines compatibility between sub- and superclasses and introduces the notion of views in the sense of hiding parts of a class description. It turns out that a view has the same properties as a (virtual) superclass.},
  volume = {858}
}

@inproceedings{Engels94,
  author = {Gregor Engels AND Hartmut Ehrig},
  title = {Towards a Module Concept for Graph Transformation Systems: The Software Engineering Perspective},
  booktitle = {Proceedings Colloquium on Graph Transformation and its Application in Computer Science},
  year = {1994},
  editor = {G. Valiente Feruglio and F. Rossello Llompart},
  publisher = {Universitat de les Illes Balears, Departament de Ci},
  month = {M{\"a}rz},
  series = {Technical Report },
  volume = {B-19}
}

@inproceedings{Engels1993,
  author = {Gregor Engels AND A.A. Verrijn-Stuart},
  title = {Integrationsaspekte bei verteilter Software-Entwicklung},
  booktitle = {Fortschritt-Berichte VDI},
  year = {1993},
  pages = {45--53},
  publisher = {VDI Verlag},
  month = {October},
  series = {Reihe 10: Informatik/Kommunikationstechnik}
}

@inproceedings{Koopman1992,
  author = {Pieter Koopman AND Luuk Groenewegen AND Gregor Engels},
  title = {Functional Description of Parallel Processes},
  booktitle = {Proceedings of the conference SION Computing Science in the Netherlands (CSN '92), The Netherlands},
  year = {1992},
  editor = {J.L.G. Dietz},
  pages = {156--167},
  note = {SION}
}

@inproceedings{Hohenstein1990,
  author = {Uwe Hohenstein AND Gregor Engels},
  title = {Formal Semantics of an Entity-Relationship Query Language},
  booktitle = {Proceedings of the 9th International Conference on Entity-Relationship Approach (ER 90), Lausanne, Switzerland},
  year = {1990},
  editor = {H. Kangassalo},
  pages = {177--188},
  publisher = {ER Institute},
  month = {October}
}

@inproceedings{Engels1989a,
  author = {Gregor Engels},
  title = {CADDY-O: Syntaxgest{\"u}tztes, graphisches Entwerfen konzeptioneller Datenbankschemata},
  booktitle = {Tagungsband GI-Fachtagung "Interaktive Schnittstellen f{\"u}r Informationssysteme", TU Clausthal, Notizen zu Interaktive Systeme},
  year = {1989},
  editor = {A. Heuer, I. Kupka},
  pages = {1-16},
  month = {November},
  volume = {18}
}

@inproceedings{Engels1989b,
  author = {Gregor Engels AND Uwe Hohenstein AND Klaus H{\"u}lsmann AND Perdita L{\"o}hr-Richter AND Hans-Dietrich Ehrich},
  title = {CADDY: Computer-Aided Design of Non-Standard Databases},
  booktitle = {Proceedings of the International Conference on System Development Environments \& Factories, Berlin, Germany},
  year = {1989},
  editor = {N. Madhavji, W. Sch{\"a}fer, H. Weber},
  publisher = {Pitman Publishing},
  address = {Berlin},
  month = {May}
}

@inproceedings{Ebert1989,
  author = {J{\"u}rgen Ebert AND Gregor Engels},
  title = {Konzepte einer Software-Architektur-Beschreibungssprache},
  booktitle = {Software-Entwicklung: Konzepte, Erfahrungen, Perspektiven, Fachtagung, 1989, Marburg (Germany)},
  year = {1989},
  editor = {W.-M. Lippe},
  pages = {238--250},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {June},
  series = {Informatik-Fachberichte},
  volume = {212}
}

@inproceedings{Engels1988,
  author = {Gregor Engels AND Thorsten Janning AND Wilhelm Sch{\"a}fer},
  title = {A Highly Integrated Tool Set for Program Development Support},
  booktitle = {Proceedings of the conference on ACM SIGSMALL/PC symposium on ACTES (SIGSMALL 1988), Cannes (France)},
  year = {1988},
  pages = {1--10},
  publisher = {ACM Press},
  address = {New York, NY, USA},
  note = {SIGSMALL '88: Proceedings of the 1988 ACM SIGSMALL/PC symposium on ACTES},
  abstract = {This paper describes the design of the integrated user interface of the software development environment IPSEN (Integrated Programming Support Environment). We explain the characteristic features of the IPSEN user interface, namely the structured layout of the screen, the command-driven tool activation, and especially the highly integrated use of the IPSEN tool set. We demonstrate those features by taking a sample set of tools of the IPSEN environment. That tool set supports all the programming-in-the-small activities within IPSEN. Finally, we sketch the realization of two prototypes running on an IBM-AT and a net of SUN workstations.}
}

@inproceedings{EngelsHNSE1988a,
  author = {Gregor Engels AND Uwe Hohenstein AND Leonore Neugebauer AND Gunter Saake AND Hans-Dietrich Ehrich},
  title = {Konzeption einer integrierten Datenbank-Entwurfsumgebung},
  booktitle = {Proceedings of DBTA/SI Data Dictionaries und Entwicklungswerkzeuge f{\"u}r Datenbank-Anwendungen, Z{\"u}rich, Switzerland},
  year = {1988},
  editor = {F. Oertly},
  pages = {151--157},
  publisher = {Verlag der Fachvereine an den Schweiz. Hochschulen und Techniken}
}

@inproceedings{Engels1987,
  author = {Gregor Engels AND Andy Sch{\"u}rr},
  title = {A Hybrid Interpreter in a Software Development Environment},
  booktitle = {Proceedings of the 1st European Software Engineering Conference (ESEC '87), Strasbourg (France)},
  year = {1987},
  editor = {H.K. Nichols, D. Simpson},
  pages = {80--88},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {This paper describes the realization of an execution tool for Modula-2 modules which ispart of an integrated tool set in a software development environment termed IPSEN (IncrementalProgramming Support Environment). In this environment, all software documents, e.g.Modula-2 modules, are manipulated by syntax-directed editors and are represented internallyby attributed graphs. The execution of Modula-2 modules is done by two cooperating interpreters.The first one is a graph interpreter which traverses the internal graph from statementto statement. These statements are translated into a low-level, more efficiently executable objectcode and interpreted by a second interpreter. This concept of a hybrid interpreter allowsthe realization of an execution tool which offers a lot of runtime support features to the user.},
  volume = {289}
}

@inproceedings{EngelsNS1987a,
  author = {Gregor Engels AND Manfred Nagl AND Wilhelm Sch{\"a}fer},
  title = {On the Structure of Structure-Oriented Editors for Different Applications},
  booktitle = {Proceedings of the ACM SIGSOFT/SIGPLAN Software Engineering Symposium on Practical Software Development Environments, Palo Alto, USA},
  year = {1987},
  editor = {P. Henderson},
  pages = {190--198},
  publisher = {ACM SIGPLAN Notices},
  month = {January},
  journal = {SIGPLAN Not.},
  volume = {22}
}

@inproceedings{EngelsLNS1986b,
  author = {Gregor Engels AND Claus Lewerentz AND Manfred Nagl AND Wilhelm Sch{\"a}fer},
  title = {On the Structure of an Incremental and Integrated Software Development Environment},
  booktitle = {Proceedings of the 19th Hawaii International Conference on System Sciences, Hawaii, USA},
  year = {1986},
  pages = {585--597},
  volume = {2a}
}

@inproceedings{Engels1985a,
  author = {Gregor Engels AND Wilhelm Sch{\"a}fer},
  title = {Graph Grammar Engineering: A Method Used for the Development of an Integrated Programming Support Environment},
  booktitle = {Proceedings of the International Joint Conference on Theory and Practiceof Software Development (TAPSOFT 1985), Berlin (Germany)},
  year = {1985},
  editor = {H. Ehrig, C. Floyd, M. Nivat, J. W. Thatcher},
  pages = {179--193},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {We introduce a method to specify the functional behaviour of software tools in an incremental and integrated software development environment. This specification method is based on graph grammars. It is an adequate method to specify the behaviour of all software systems using graphs as internal data structures. We show that a specification can be developed systematically by which the adaptability of the environment is increased towards modification of tools or extension by new tools. Furthermore, guidelines for the implementation can directly be derived from this specification.},
  series = {LNCS},
  volume = {186}
}

@inproceedings{EngelsS1985m,
  author = {Gregor Engels AND Wilhelm Sch{\"a}fer},
  title = {The Design of an Adaptive and Portable Programming Support Environment},
  booktitle = {Proceedings of the International Computing Symposium, Amsterdam (The Netherlands)},
  year = {1985},
  editor = {G. Valle, G. Bucci},
  address = {Florenz}
}

@inproceedings{Pletat1982,
  author = {Udo Pletat AND Gregor Engels AND Hans-Dietrich Ehrich},
  title = {An Operational Approach to Conditional Algebraic Specifications},
  booktitle = {Proceedings of the 7eme Colloque sur les Arbres en Algebre et en Programmation, Lille (France)},
  year = {1982},
  editor = {H.J. Schneider, H. G{\"o}ttler},
  pages = {254--270},
  month = {March },
  abstract = {We suppose to give conditional specifications of abstract data types hierarchically. Considering algebraic specifications from an operational point of view this approach enables us to present simple syntactic criteria for the Church-Rosser property, which implies the welldefinedness of the operational semantics of a conditional specification. Furthermore, these criteria are sufficient for the termination of the full substitution reduction strategy. },
  volume = {82}
}

@inproceedings{Engels1982,
  author = {Gregor Engels AND Wilhelm Sch{\"a}fer},
  title = {Specification of a Programming Support Environment by Graph Grammars},
  booktitle = {Proceedings of the conference on Graphtheoretic Concepts in Computer Science (WG`82), M{\"u}nchen (Germany)},
  year = {1982},
  editor = {H.J. Schneider and H. G{\"o}ttler},
  pages = {47--62},
  publisher = {Hanser},
  address = {M{\"u}nchen/Leipzig}
}

@inproceedings{fle2013,
  author = {Masud Fazal-Baqaie AND Markus Luckey AND Gregor Engels},
  title = {Assembly-based Method Engineering with Method Patterns},
  booktitle = {Software Engineering 2013 Workshopband},
  year = {2013},
  editor = {M. Kuhrmann, D. M. Fern{'a}ndez, O. Linsen, A. Knapp},
  pages = {435-444},
  publisher = {GI, K{\"o}llen Druck+Verlag GmbH, Bonn},
  abstract = {Software development methods prescribe and coordinate the activities necessary to plan, build, and deliver software. To provide methods that account for the situational context of a development project, e.g., an acquirer-supplier-relationship or specific communication needs, the existing method creation approaches represent a trade-off between flexibility and ease of use. On the side, less flexible configurable methods offer a fixed set of configurations to quickly adapt a method to the situation at hand. On the other side, flexible assembly-based approaches allow creating methods from scratch by combining preexisting building blocks, thus are capable of creating methods not covered by configurations of configurable methods, e.g., a mixture of agile and plan-driven ideas. However, assembly-based approaches are not easy to use and require considerable expert knowledge. In this paper we suggest the use of method patterns during the assembly-based method creation. Method patterns represent desirable principles for the to-be-method and therefore support the right choice and combination of method building blocks, simplifying assembly-based method creation.},
  journal = {Software Engineering 2013 Workshopband}
}

@inproceedings{CAiSE13_Nagel,
  author = {Benjamin Nagel AND Christian Gerth AND Jennifer Post AND Gregor Engels},
  title = {Kaos4SOA - Extending KAOS Models with Temporal and Logical Dependencies},
  booktitle = {Proceedings of the Forum at the CAiSE'13 Conference on Advanced Information Systems Engineering(accepted for publication)},
  year = {2013},
  publisher = {CEUR-WS.org},
  series = {CEUR Workshop Proceedings}
}

@inproceedings{CAiSE12_Huma_Gerth,
  author = {Zille Huma AND Christian Gerth AND Gregor Engels AND Oliver Juwig},
  title = {A UML-based Rich Service Description Language for Automatic Service Discovery of Heterogeneous Service Partners},
  booktitle = {Proceedings of the Forum at the CAiSE'12 Conference on Advanced Information Systems Engineering},
  year = {2012},
  pages = {90--97},
  publisher = {CEUR-WS.org},
  abstract = {Service-oriented computing (SOC) emerges as a promising trend solving many issues in distributed software development. Followingthe essence of SOC, service descriptions are dened by the service partners in their independent heterogeneous domains based on current standards, such as, WSDL. However, these standards are mostly syntacticand do not provide any semantic description which may lead to inaccurate service discovery results. Currently many research efforts aim at formulating rich service descriptions for service partners comprisingsyntactic as well as semantic information. However, due to the underlying heterogeneity of service partners in terms of different underlying ontologies, different description notations, etc., matching of rich servicedescriptions for accurate service discovery is a complex task. In this paper, we come up with a proposal for rich service descriptions based on the UML.},
  series = {CEUR Workshop Proceedings},
  volume = {855}
}

@inproceedings{Arifulina2012a,
  author = {Svetlana Arifulina AND Christian Soltenborn AND Gregor Engels},
  title = {Coverage Criteria for Testing DMM Specifications},
  booktitle = {Proceedings of the 11th International Workshop on Graph Transformation and Visual Modeling Techniques (GT-VMT 2012), Tallinn (Estonia)},
  year = {2012},
  editor = {A. Fish, L. Lambers},
  publisher = {European Association of Software Science and Technology (EASST)},
  abstract = {Behavioral modeling languages are most useful if their behavior is specified formally such that it can e.g. be analyzed and executed automatically. Obviously, the quality of such behavior specifications is crucial. The rule-based semantics specification technique Dynamic Meta Modeling (DMM) honors this by using the approach of Test-driven Semantics Specification (TDSS), which makes sure that the specification at hand at least describes the correct behavior for a suite of test models. However, in its current state TDSS does not provide any means to measure the quality of such a test suite.In this paper, we describe how we have applied the idea of test coverage to TDSS. Similar to common approaches of defining test coverage criteria, we describe a data structure called invocation graph containing possible orders of applications of DMM rules. Then we define different coverage criteria based on that data structure, taking the rule applications caused by the test suite's models into account. Our implementation of the described approach gives the language engineer using DMM a means to reason about the quality of the language's test suite, and also provides hints on how to improve that quality by adding dedicated test models to the test suite.},
  series = {Electronic Communications of the EASST},
  volume = {47}
}

@inproceedings{Geisen_Luckey092012,
  author = {Silke Geisen AND Markus Luckey AND Gregor Engels},
  title = {Ein Ansatz zur dynamischen Qualit{\"a}tsmessung,-bewertung und Anpassung von Software Engineering Methoden},
  booktitle = {Proceedings of 19. GI-WIVM Workshop: Qualit{\"a}tsmanagement und Vorgehensmodelle},
  year = {2012},
  pages = {111-120},
  publisher = {Shaker Verlag},
  month = {September},
  abstract = {Damit die erfolgreiche Entwicklung einer Software und damit der Erfolg eines Projektes gew{\"a}hrleistet ist, wird h{\"a}ufig eine Software Engineering Methode (SEM) zu Beginn auf die Projektsituation abgestimmt. Doch w{\"a}hrend der Durchf{\"u}hrung der Software Engineering Methode k{\"o}nnen {\"A}nderungen an der Projektsituation oder mangelnde Qualit{\"a}t den Projekterfolg gef{\"a}hrden. Diese Situationen machen eine dynamische Anpassung der SEM, insbesondere zur Erreichung der Qualit{\"a}tsziele, erforderlich. Bekannte Verbesserungs- bzw. Anpassungsverfahren wie Six Sigma oder dem Deming Cycle sind aufgrund ihrer langen Durchf{\"u}hrungsdauer kaum f{\"u}r eine solche Anpassung geeignet. Ferner finden diese Verfahren typischerweise nach einem Projekt statt und betrachten selten {\"A}nderungen an der aktuellen Projektsituation oder die Qualit{\"a}t der SEM w{\"a}hrend der Durchf{\"u}hrung. Agile Methoden wie Scrum nutzen erste M{\"o}glichkeiten zur Inspektion und Anpassung im laufenden Projekt. Diese Idee soll aufgegriffen und weiter verbessert werden. Im Gegensatz zu Six Sigma und dem Deming Cycle beobachten Ans{\"a}tze aus dem Autonomic Computing zur Laufzeit selbstst{\"a}ndig Systeme {\"u}ber Feedbackschleifen und passen das System gegebenenfalls an. Das bekannteste Modell ist die sogenannte MAPE-K Schleife. Diese Arbeit stellt einen Ansatz vor, wie sich die MAPE-K Schleife f{\"u}r die dynamische Anpassung von Software Engineering Methoden sowie zur kontinuierlichen Qualit{\"a}tsmessung und Bewertung nutzen l{\"a}sst.}
}

@inproceedings{nagel_mdhpcl12,
  author = {Benjamin Nagel AND Christian Gerth AND Enes Yigitbas AND Fabian Christ AND Gregor Engels},
  title = {Model-driven Specification of Adaptive Cloud-based Systems},
  booktitle = {Proceedings of 1st International Workshop on Model-Driven Engineering for High Performance and Cloud Computing (MDHPCL) at MODELS'12},
  year = {2012}
}

@inproceedings{luckey_eval4saso12,
  author = {Markus Luckey AND Christian Thanos AND Christian Gerth AND Gregor Engels},
  title = {Multi-Staged Quality Assurance for Self-Adaptive Systems},
  booktitle = {Proceedings of 1st International Workshop on EVALUATION for SELF-ADAPTIVE and SELF-ORGANIZING SYSTEMS at SASO'12 (to appear)},
  year = {2012}
}

@inproceedings{brueseke2011a,
  author = {Frank Br{\"u}seke AND Steffen Becker AND Gregor Engels},
  title = {Palladio-based performance blame analysis},
  booktitle = {Proceedings of the 16th International Workshop on Component-Oriented Programming (WCOP; satellite event of the CompArch 2011), Boulder Colorado, CO (USA)},
  year = {2011},
  editor = {R. Reussner, C. Szyperski, W. Weck},
  pages = {25-32},
  publisher = {ACM},
  address = {New York, NY (USA)},
  abstract = {Performance is an important quality attribute for business information systems. When a tester has spotted a performance error, the error is passed to thesoftware developers to fix it. However, in component-based software development the tester has to do blame analysis first, i. e. the tester has to decide, which party is responsible to fix the error. If the error is a design or deployment issue, itcan be assigned to the software architect or the system deployer. If the erroris specific to a component, it needs to be assigned to the corresponding component developer. An accurate blame analysis is important, because wrong assignments of errors will cause a loss of time and money. Our approach aims at doing blame analysis for performance errors by comparing performance metrics obtained in performance testing and performance prediction. We use performance prediction values as expected values for individual components. For performance prediction we use the Palladio approach. By this means, our approach evaluates each component's performance in a certain test case. If thecomponent performs poorly, its component developer needs to fixthe component or the architect replaces the component with afaster one. If no omponent performs poorly, we can deduce that there is a design or deployment issue and the architecture needs to be changed. In this paper, we present an exemplary blame analysis based on a web shop system. The example shows the feasibility of our approach. }
}

@inproceedings{bruSanEng2010_sqmb,
  author = {Frank Br{\"u}seke AND Yavuz Sancar AND Gregor Engels},
  title = {Architecture-Driven Derivation of Performance Metrics},
  booktitle = {Proceedings of Software-Qualit{\"a}tsmodellierung und -bewertung (SQMB '10), Paderborn, Germany},
  year = {2010},
  editor = {Wagner, S.; Broy, M.; Deissenboeck, F. ; M{\"u}nch, J.; Liggesmeyer, P.},
  pages = {22-31},
  publisher = {Technische Universit{\"a}t M{\"u}nchen},
  address = {M{\"u}nchen, Germany}
}

@inproceedings{SSEB10,
  author = {Frank Salger AND Stefan Sauer AND Gregor Engels AND Andrea Baumann},
  title = {Knowledge Transfer in Global Software Development - Leveraging Ontologies, Tools and Assessments},
  booktitle = {5th IEEE International Conference on Global Software Engineering (ICGSE 2010)},
  year = {2010},
  pages = {336--341},
  month = {August},
  abstract = {To be successful with global software development (GSD), development knowledge needs to be shared among the developers and stakeholders, and the quality of the exchanged information must be assured. Therefore, mature processes, methods and tools have to be in place. If a unified and integrated solution does not exist, this impedes the exchange of knowledge (and the migration of people between projects). In GSD, such a diversity can lead to new problems: offshore development teams have to repeatedly re-adjust to method variants used by the respective business units. This can lead to misinterpretation of information and risks for project success. We report on re-aligning the varying software engineering methods and unifying the methodology throughout Capgemini sd\&m. We also standardized quality assurance procedures and tightly integrated them with the engineering methodology. By this, we arrived at a comprehensive company-wide Enterprise Software Engineering Model that effectively supports knowledge transfer from clients to the onshore and offshore team.}
}

@inproceedings{EngelsSoltenborn2010a,
  author = {Gregor Engels AND Christian Soltenborn},
  title = {Test-driven Language Derivation with Graph Transformation-based Dynamic Meta Modeling},
  booktitle = {Proceedings of the International Colloquium on Graph and Model Transformation (GraMoT 2010), Berlin (Germany)},
  year = {2010},
  editor = {C. Ermel, H. Ehrig, F. Orejas, G. Taentzer},
  pages = {240--257},
  publisher = {European Association of Software Science and Technology},
  abstract = {Deriving a new language L\_B from an already existing one L\_A is a typical task in domain-specific language engineering. Here, besides adjusting L\_A's syntax, the language engineer has to modify the semantics of L\_A to derive L\_B's semantics. Particularly, in case of behavioral modeling languages, this is a difficult and error-prone task, as changing the behavior of language elements or adding behavior for new elements might have undesired side effects.Therefore, we propose a test-driven language derivation process. In a first step, the language engineer creates example models containing the changed or newly added elements in different contexts. For each of these models, the language engineer also precisely describes the expected behavior. In a second step, each example model and its description of behavior is transformed into an executable test case. Finally, these test cases are used when deriving the actual semantics of L\_B - at any time, the language engineer can run the tests to verify whether the changes he performed on L\_A's semantics indeed produce the desired behavior. In this paper, we illustrate the approach using our graph transformation-based semantics specification technique Dynamic Meta Modeling. This is once more an example where the graph transformation approach shows its strengths and appropriateness to support software engineering tasks as, e.g.,model transformations, software specifications, or tool development.},
  series = {Electronic Communications of the EASST},
  volume = {30}
}

@inproceedings{SQMB10TQ,
  author = {Yavuz Sancar AND Frank Br{\"u}seke AND Gregor Engels},
  title = {Teststufenspezifische Qualit{\"a}tsattribute f{\"u}r die Qualit{\"a}tsbewertung von nichtfunktionalen Anforderungen},
  booktitle = {Proceedings of Software-Qualit{\"a}tsmodellierung und -bewertung (SQMB '10), Paderborn, Germany},
  year = {2010},
  editor = {Wagner, S.; Broy, M.; Deissenboeck, F. ; M{\"u}nch, J.; Liggesmeyer, P.},
  pages = {50-57},
  publisher = {Technische Universit{\"a}t M{\"u}nchen},
  address = {M{\"u}nchen, Germany}
}

@inproceedings{Etoos2010,
  author = {Yavuz Sancar AND Frank Br{\"u}seke AND Hendrik Voigt AND Stefan Sauer AND Gregor Engels},
  title = {Towards Economical Software Release Recommendations},
  booktitle = {ECOOP 2010 - Workshop on Testing Object-Oriented Software Systems (ETOOS)},
  year = {2010},
  pages = {59-67},
  month = {June}
}

@inproceedings{Salger2009b,
  author = {Frank Salger AND Stefan Sauer AND Gregor Engels},
  title = {An Integrated Quality Assurance Framework for Specifying Business Information Systems},
  booktitle = {Proceedings of the Forum at the CAiSE 2009 Conference, Amsterdam (The Netherlands)},
  year = {2009},
  editor = {E. Yu, J. Eder, C. Rolland},
  pages = {25--30},
  publisher = {CEUR},
  abstract = {The software specification acts as a bridge between customers, architects, software developers and testers. If information gets lost or distorted when building this bridge, the wrong system will be built or the system will not be built in time and budget--or both! Standards and recommendations give advice on how to structure specifications or check software-engineering artefacts with reviews or inspections. But these constructive and analytical approaches are not well integrated with each other. Moreover, they are often too generic to efficiently support the specification of particular system types. In this paper, we present the integrated ``specification framework'' of Capgemini sd\&m. It consists of our specification method for business information systems (BIS) and its concerted analytical counterpart, the ``specification quality gate''. Since this framework is tailored to the specification of large BIS, it allows a quick ramp-up phase for software engineering projects without the need for extensive tailoring or extension.},
  volume = {453}
}

@inproceedings{EngAuto09,
  author = {Gregor Engels},
  title = {Automatic Generation of Behavioral Code - too ambitious or even unwanted?},
  booktitle = {First European Workshop on Behaviour Modelling in Model Driven Architecture (BM-MDA)},
  year = {2009},
  editor = {M. Aksit, E. Kindler, A. McNeile, E. Roubtsova},
  pages = {5},
  publisher = {ACM Press (New York, NY, USA)},
  address = {New York, NY, USA}
}

@inproceedings{modevva09,
  author = {Michael Mlynarski AND Baris G{\"u}ldali AND Melanie Sp{\"a}th AND Gregor Engels},
  title = {From Design Models to Test Models by Means of Test Ideas},
  booktitle = {MoDeVVa '09: Proceedings of the 6th International Workshop on Model-Driven Engineering, Verification and Validation},
  year = {2009},
  editor = {L. L{'u}cio and S. Wei{\ss}leder},
  pages = {1-10},
  publisher = {ACM},
  address = {New York, NY, USA},
  abstract = {Model-Based Testing is slowly becoming the next level of software testing. It promises higher quality, better coverage and efficient change management. MBT shows two main problems of modeling the test behavior. While modeling test cases test designers rewrite most of the system specification. Further, the number of test cases generated by modern tools is often not feasible. In practice, both problems are not solved. Assuming that the functional design is based on models, we show how to use them for software testing. With so-called test ideas, we propose a way to manually select and automatically transform the relevant parts of the design model into a basic test model that can be used for test case generation. We give an example and discuss the potentials for tool support. }
}

@inproceedings{Salger2009a,
  author = {Frank Salger AND Gregor Engels AND Alexander Hofmann},
  title = {Inspection Effectiveness for Different Quality Attributes of Software RequirementSpecifications - An Industrial Case Study},
  booktitle = {Proceedings of the ICSE Workshop on Software Quality (WoSQ 2009)},
  year = {2009},
  pages = {15--21}
}

@inproceedings{Soltenborn2009c,
  author = {Christian Soltenborn AND Gregor Engels},
  title = {Towards Generalizing Visual Process Pattern},
  booktitle = {Proceedings of the 1st International Workshop on Visual Formalisms for Patterns (VFfP 2009), Corvallis, OR (USA)},
  year = {2009},
  editor = {P. Bottoni, E. Guerra, J. de Lara, T. Margaria, J. Padberg, G. Taentzer},
  publisher = {European Association of Software Science and Technology},
  abstract = {Visual Process Pattern (VPP) is a visual language to describe constraints on the behavior of UML Activities. They have been developed for the sake of formulating and verifying requirements on business process models (with Activities being one possible description language). In the VPP approach, a visual pattern is translated into an LTL formula, which can then be verified against a transition system describing the behavior of the Activity under consideration.In this paper, we aim at generalizing VPP. We show how to formulate patterns more generally, using either concrete or abstract syntax of the behavioral model under consideration. Additionally, we describe how these more general patterns can be verified against a model's behavior.},
  series = {Electronic Communications of the EASST},
  volume = {25}
}

@inproceedings{Kuester08,
  author = {Jochen K{\"u}ster AND Christian Gerth AND Alexander F{\"o}rster AND Gregor Engels},
  title = {A Tool for Process Merging in Business-Driven Development},
  booktitle = {Proceedings of the Forum at the CAiSE'08 Conference on Advanced Information Systems Engineering},
  year = {2008},
  editor = {Z. Bellahs{\`e}ne, R. Coletta, X. Franch, E. Hunt, C. Woo},
  pages = {89--92},
  publisher = {CEUR-WS.org},
  abstract = {Business-driven development favors the construction of process modelsat different abstraction levels and by different people. As a consequence, thereis a demand for consolidating different versions of process models by mergingthem. In this paper, we study a basic scenario, derive requirements and present aprototype for detecting and resolving changes between process models.},
  series = {CEUR Workshop Proceedings},
  volume = {344}
}

@inproceedings{MOTES08,
  author = {Jens Ellerweg AND Gregor Engels AND Baris G{\"u}ldali},
  title = {Modellbasierter Komponententest mit visuellen Kontrakten},
  booktitle = {INFORMATIK 2008, Beherrschbare Systeme - dank Informatik, Band 1, Beitr{\"a}ge der 38. Jahrestagung der Gesellschaft f{\"u}r Informatik e.V. (GI)},
  year = {2008},
  editor = {H.-G. Hegering, A. Lehmann, H. J. Ohlbach, C. Scheideler},
  pages = {211--214},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  series = {Lecture Notes in Informatics},
  volume = {133}
}

@inproceedings{Soltenborn2006,
  author = {Christian Soltenborn AND Gregor Engels},
  title = {Analysis of UML Activities with Dynamic Meta Modeling Techniques},
  booktitle = {Symposium "A Formal Semantics for UML" (satellite event of the MoDELS conference 2006), Genova (Italy)},
  year = {2007},
  editor = {T. K{\"u}hne},
  pages = {329--330},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Based on a semantics of UML Activities specified with the Dynamic Meta Modeling approach, we analyze the dynamic semantics of Activities at modeling time.},
  series = {LNCS},
  volume = {4364}
}

@inproceedings{Engels2006a,
  author = {Gregor Engels AND Baris G{\"u}ldali AND Marc Lohmann},
  title = {Towards Model-Driven Unit Testing},
  booktitle = {Proceedings of the 2006 International Conference on Models in Software Engineering (MoDELS 2006)},
  year = {2007},
  editor = {T. K{\"u}hne},
  pages = {182--192},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  note = {Models in Software Engineering, Workshops and Symposia at MoDELS 2006, Genoa, Italy, October 1-6, 2006, Reports and Revised Selected Papers, Genua (Italy)},
  abstract = {The Model-Driven Architecture (MDA) approach for constructingsoftware systems advocates a stepwise refinement and transformationprocess starting from high-level models to concrete programcode. In contrast to numerous research efforts that try to generate executablefunction code from models, we propose a novel approach termedmodel-driven monitoring. On the model level the behavior of an operationis specified with a pair of UML composite structure diagrams (visualcontract), a visual notation for pre- and post-conditions. The specifiedbehavior is implemented by a programmer manually. An automatic translationfrom our visual contracts to JML assertions allows for monitoringthe hand-coded programs during their execution.In this paper we present an approach to extend our model-driven monitoringapproach to allow for model-driven unit testing. In this approachwe utilize the generated JML assertions as test oracles. Further, wepresent an idea how to generate sufficient test cases from our visualcontracts with the help of model-checking techniques.},
  series = {LNCS},
  volume = {4364}
}

@inproceedings{EngelsGS2006c,
  author = {Gregor Engels AND Matthias Gehrke AND Stefan Sauer},
  title = {Multi-Private Public Partnership (MPPP) - Softwaretechnik auf dem Weg in die Industrie},
  booktitle = {Proceedings of the Workshop on Vernetzung von Software Engineering Expertise in Industrie und Forschung (VSEEIF, satellite event of the Informatik 2006 - Informatik f{\"u}r Menschen)},
  year = {2006},
  editor = {C. Hochberger, R. Liskowsky},
  pages = {281--287},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  note = {Proceedings of Workshop Vernetzung von Software Engineering Expertise in Industrie und Forschung (VSEEIF), Informatik 2006 - Informatik f{\"u}r Menschen Band 1},
  series = {Lecture Notes in Informatics},
  volume = {93}
}

@inproceedings{Engels2006b,
  author = {Gregor Engels AND Baris G{\"u}ldali AND Marc Lohmann},
  title = {Towards Model-Driven Unit Testing},
  booktitle = {Proceedings of the workshop on Model Design and Validation (MoDeVa 2006), Toulouse (France)},
  year = {2006},
  editor = {D. Hearnden, J.G. S{\"u}{\ss}, N. Rapin, B. Baudry},
  pages = {16--29},
  publisher = {Le Commissariat {\`a} l'Energie Atomique - CEA},
  address = {Berlin / Heidelberg},
  month = {October},
  abstract = {The Model-Driven Architecture (MDA) approach for constructing software systems advocates a stepwise refinement and transformation process starting from high-level models to concrete program code. In contrast to numerous research efforts that try to generate executable function code from models, we propose a novel approach termed model-driven monitoring. On the model level the behavior of an operation is specified with a pair of UML composite structure diagrams (visual contract), a visual notation for pre- and post-conditions. The specified behavior is implemented by a programmer manually. An automatic translation from our visual contracts to JML assertions allows for monitoring the hand-coded programs during their execution. In this paper we present an approach to extend our model-driven monitoringapproach to allow for model-driven unit testing. In this approach we utilize the generated JML assertions as test oracles. Further, we present an idea how to generate sufficient test cases from our visual contracts with the help of model-checking techniques.}
}

@inproceedings{Frohnhoff06,
  author = {Stephan Frohnhoff AND Volker Jung AND Gregor Engels},
  title = {Use Case Points in der industriellen Praxis},
  booktitle = {Proceedings of the International Workshop on Software Metrics and DASMA Software Metrik Kongress (IWSM/MetriKon 2006), Potsdam (Germany)},
  year = {2006},
  editor = {A. Abran, M. Bundschuh, G. B{\"u}ren, R. Dumke},
  pages = {511--526},
  publisher = {Magdeburger Schriften zum Empirischen Software-Engineering},
  note = {Applied Software Measurement: Proc. International Workshop on Software Metrics and DASMA Software Metrik Kongress IWSM/MetriKon 2006}
}

@inproceedings{Engels2005b,
  author = {Gregor Engels AND Marc Lohmann AND Stefan Sauer},
  title = {Design by Contract zur semantischen Beschreibung von Web Services},
  booktitle = {Proceedings of Informatik 2005 - Informatik LIVE! Band 2, Beitr{\"a}ge der 35. Jahrestagung der Gesellschaft f{\"u}r Informatik e.V. (GI), Workshop Service-orientierte Architekturen - Zusammenwirken von Business \& IT, Bonn (Germany)},
  year = {2005},
  editor = {A. B. Cremers, R. Manthey, P. Martini, V. Steinhage},
  pages = {612--616},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {September },
  abstract = {Die Vision von Web Services ist, dass ein Service Requestor einen Ser-vice Provider dynamisch finden und binden kann. F{\"u}r das Finden eines Web Ser-vices m{\"u}ssen die Anforderungen eines Requestors und die Beschreibung eines Services miteinander verglichen werden. Syntaktische Beschreibungen reichen hierf{\"u}r nicht aus. Eine M{\"o}glichkeit zur semantischen Beschreibung von Web Ser-vices basiert auf der Technik Design by Contract. In diesem Papier f{\"u}hren wir eine UML-basierte Notation f{\"u}r Kontrakte sowie ein Matching-Konzept ein. Damit wird eine automatisierte, semantische Suche nach Web Services m{\"o}glich.},
  series = {Lecture Notes in Informatics},
  volume = {68}
}

@inproceedings{EngelsLS2005c,
  author = {Gregor Engels AND Marc Lohmann AND Stefan Sauer},
  title = {Modellbasierte Entwicklung von Web Services mit Design by Contract},
  booktitle = {Proceedings of Informatik 2005 - Informatik LIVE! Band 2, Beitr{\"a}ge der 35. Jahrestagung der Gesellschaft f{\"u}r Informatik e.V. (GI), Workshop Modellbasierte Qualit{\"a}tssicherung, Bonn, Germany},
  year = {2005},
  editor = {A. B. Cremers, R. Manthey, P. Martini, V. Steinhage},
  pages = {491--495},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  abstract = {Die Qualit{\"a}t Service-orientierter Softwaresysteme h{\"a}ngt wesentlich von der Einbindung der richtigen Dienste ab. Zwei grunds{\"a}tzliche Aspekte kommen hierbei zum Tragen: (1) Passen die Anforderungen eines Service Requestors und die Servicebeschreibung eines Service Providers zusammen und (2) ist die Imple-mentierung der Web Services korrekt gegen{\"u}ber der Servicebeschreibung. Wir verwenden Design by Contract Techniken auf der Modellebene zur semantischen Beschreibung von Web Services und f{\"u}hren ein Matching-Konzept f{\"u}r den Ver-gleich von Requestor- und Provider-Kontrakten ein. Damit wird eine automatisier-te, semantische Suche nach Web Services m{\"o}glich. Wir erl{\"a}utern zudem eine mo-dellbasierte Vorgehensweise zur Entwicklung von Web Services. Hierbei werden aus den Modellen der Anwendung (1) die auswertbaren semantischen Beschrei-bungen und (2) Runtime-Assertions erzeugt, um die Korrektheit der Implementie-rung eines Web Services gegen{\"u}ber seiner Spezifikation zu {\"u}berpr{\"u}fen. So wird eine konstruktive und pr{\"u}fende Qualit{\"a}tssicherung unterst{\"u}tzt.},
  series = {Lecture Notes in Informatics},
  volume = {68}
}

@inproceedings{Chrechago2005,
  author = {Alexey Cherchago AND Gregor Engels},
  title = {Preservation of Compatibility under Evolution of Software Components},
  booktitle = {International ERCIM-ESF Workshop on Challenges in Software Evolution (ChaSE 2005), Berne (Switzerland)},
  year = {2005},
  month = {April}
}

@inproceedings{Foerster2003,
  author = {Alexander F{\"o}rster AND Gregor Engels},
  title = {Quality Ensuring Development of Software Processes},
  booktitle = {Proceeding of the 9th European Workshop on Software Process Technology (EWSPT 2003), Helsinki (Finland)},
  year = {2003},
  editor = {F. Oquendo},
  pages = {62--73},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  series = {LNCS},
  volume = {2786}
}

@inproceedings{Thone2002,
  author = {Sebastian Th{\"o}ne AND Ralph Depke AND Gregor Engels},
  title = {Process-Oriented, Flexible Composition of Web Services with UML},
  booktitle = {Proceedings of the International Workshop on Conceptual Modeling Approaches for e-Business: A Web Service Perspective (eCOMO 2002), Tampere (Finland)},
  year = {2002},
  pages = {390--401},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  abstract = {The composition of elementary web services to larger-scale services has become an important means to enhance e-business collaborations. If such composite web services can also integrate legacy components that are not yet provided as web services, the number of possible compositions is increased. Following a process-oriented approach, the compositions can be described as control- and data-flow between available web services and components. This paper discusses the Business Process Execution Language for Web Services (BPEL4WS), an existing service composition language, and proposes UML-WSC as an alternative, visual language. For the advanced description of service interfaces, UML-WSC extends the type system of the established Web Service Definition Language (WSDL).},
  series = {LNCS},
  volume = {2784}
}

@inproceedings{Heckel2002139,
  author = {Reiko Heckel AND Gregor Engels},
  title = {Towards a Formal Framework for Inter-Enterprise Application Integration},
  booktitle = {Proceedings of the Closing Workshop of the TMR Network GETGRATS (2002), Bordeaux (France)},
  year = {2002},
  editor = {A. Corradini, M. Bauderon},
  pages = {139--151},
  publisher = {Elsevier},
  month = {Juni },
  abstract = {A major concern of software development today is the integration of applications of different enterprises, e.g., over the internet. This requires a shift of focus from system development towards integration of enterprise models and evolution of systems. We propose a conceptual framework for a method addressing these issues and discuss its formalization by means of graph transformation concepts.},
  series = {Electronic Notes in Theoretical Computer Science},
  volume = {51}
}

@inproceedings{Engels02,
  author = {Gregor Engels AND Jochen K{\"u}ster AND Reiko Heckel},
  title = {Towards Consistency-Preserving Model Evolution},
  booktitle = {Proceedings of the International Workshop on Principles of Software Evolution(satellite event of the ICSE 02), Orlando, Florida (USA)},
  year = {2002},
  pages = {129--132},
  publisher = {ACM Press},
  address = {New York, NY, USA},
  month = {May}
}

@inproceedings{EngelsK2001c,
  author = {Gregor Engels AND Jochen K{\"u}ster},
  title = {Enhancing UML-RT Concepts for Behavioral Consistent Architecture Models},
  booktitle = {Proceedings of the 1st Workshop on Describing Software Architecture with UML (satellite event of the ICSE 2001), Toronto (Canada)},
  year = {2001},
  month = {May}
}

@inproceedings{Busatto2000,
  author = {Giorgio Busatto AND Gregor Engels AND Katharina Mehner AND Annika Wagner},
  title = {A Framework for Adding Packages to Graph Transformation Approaches},
  booktitle = {Selected Papers of the 6th International Workshop on Theory and Application of Graph Transformations (TAGT '98), Paderborn (Germany)},
  year = {2000},
  editor = {H. Ehrig, G. Engels, H.-J. Kreowski, G. Rozenberg},
  pages = {352--367},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Graphs are a commonly used formalism for modeling many different kinds of static and dynamic data. In many applications, data modeling can be improved by using hierarchically structured graphs. But, while there already exist hierarchical graph data models, no general-purpose hierarchical graph data model exists yet, which unifies common features of these domain-specific models. In this paper, we presentgraph packages, a general formalism for defining hierarchical graphs, supporting the most important features found in known applications.Because of the dynamic nature of graphs, hierarchical graph transformation is also an important issue to be dealt with when using hierarchical graphs. Motivated by the successful application of graph grammars to the specification of graph transformations, we also introduce a framework that allows to specify hierarchical graph transformations by combining existing graph grammar approaches and our graph package concept. These concepts are a step towards the definition of a general-purpose hierarchical graph data model.},
  series = {LNCS},
  volume = {1764}
}

@inproceedings{Zamperoni2000,
  author = {Gregor Engels AND Andreas Zamperoni},
  title = {Formal Integration of Software Engineering Aspects Using Graph Rewrite Systems - A Typical Experience?!},
  booktitle = {Proceedings of the International Workshop on Applications of Graph Transformations with Industrial Relevance (AGTIVE 1999), Kerkrade (The Netherlands)},
  year = {2000},
  editor = {M. Nagl, A. Sch{\"u}rr, M. M{\"u}nch},
  pages = {359--368},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {September },
  abstract = {This position paper weighs the benefits against the problems of using a graph rewrite system for the formal specification of an integrated software engineering model and for its implementation using the same graph rewrite system. The integrated software engineering approach, called GRIDS1, has been motivated by the shortcomings of software engineering support for real-life software projects. It is based on the formal integration of software engineering aspects for the automatic construction and well-defined manipulation of situational project frameworks. GRIDS uses the graph rewrite system PROGRES for the formal specification of the concepts and for their prototypical implementation. Without claiming to cover the entire field of graph rewrite systems, the experiences of this particular, graph-based approach are used as example for a discussion about the adequacy, the benefits, but also the shortcomings and the problems of applying a graph rewrite approach to realize automated software and method engineering support.},
  series = {LNCS},
  volume = {1779}
}

@inproceedings{Engels2000d,
  author = {Gregor Engels AND Reiko Heckel},
  title = {From Trees to Graphs: Defining the Semantics of Diagram Languages with Graph Transformation},
  booktitle = {Proceedings of the Workshop on Graph Transformation and Visual Modeling Techniques (satellite events of the ICALP 2000), Geneva(Switzerland)},
  year = {2000},
  editor = {J.D.P. Rolim et al.},
  pages = {373--382},
  publisher = {Carleton Scientific},
  month = {July},
  abstract = {In order to define the semantics of diagram languages, new techniques may be developed following the established approaches of denotational, operational, or algebraic semantics of programming languages. Due to the multi-dimensional nature of diagrams (as opposed to the linear structure of programs), these new approaches should be based on graphs (rather than trees or terms) and graph transformation could provide the underlying technology. In this paper, we try to substantiate this claim by reviewing some of the most important approaches to semantics and discussing their applicability to diagram languages.}
}

@inproceedings{Engels2000f,
  author = {Gregor Engels AND Jochen K{\"u}ster AND Luuk Groenewegen},
  title = {Modeling Concurrent Behavior through Consistent Statechart Views},
  booktitle = {Proceedings of the Workshop on Dynamic Behaviour in UML Models: Semantic Questions, Munich (Germany)},
  year = {2000},
  editor = {G. Reggio, A. Knapp, B. Rumpe, B. Selic, R. Wieringa},
  pages = {44--49},
  publisher = {Ludwig-Maximilians-University},
  address = {Munich (Germany)},
  month = {October},
  abstract = {In concurrent systems, multiple components communicate with eachother by exchanging messages. Each component may take part inseveral communication protocols at the same time, each one takingpart over a so-called connector. Valid sequences of message exchangesare usually modeled in a communication protocol. There arise severalimportant questions concerning protocols: Given a protocol how toensure that each participant conforms to the protocol on the model level?Conversely, given multiple components how to extract the protocol?In our position statement, we propose a technique for ensuringprotocol conformity based on extraction of statechart views fromeach component's statechart.}
}

@inproceedings{Engels1999b,
  author = {Gregor Engels AND Reiko Heckel AND Stefan Sauer},
  title = {Dynamic Meta Modelling: A Graphical Approach to Operational Semantics},
  booktitle = {Proceedings of the workshop on Rigorous Modeling and Analysis with the UML: Challenges and Limitations (satellite event of the Conference on Onject-Oriented Programming, Systems, Languages, and Applications (OOPSLA 1999)), Denver, CO (USA)},
  year = {1999},
  abstract = {In this paper, dynamic meta modeling is proposed as a new approach to the operational semantics of behavioral UML diagrams. The dynamic meta model extends the well-known static meta model by a specification of the system's dynamics by means of collaboration diagrams.In this way, it is possible to define the behavior of UML diagrams within UML. The conceptual idea is inherited from Plotkin's structured operational semantics (SOS) paradigm, a style of semantics specification for concurrent programming languages and process calculi: Collaboration diagrams are used as deduction rules to specify a goal-oriented interpreter for the language. The approach is exemplified using a fragment of UML statechart and object diagrams.Formally, collaboration diagrams are interpreted as graph transformation rules. In this way, dynamic UML semantics can be both mathematically rigorous so as to enable formal specifications and proofs and, due to the use of UML notation, understandable without prior knowledge of heavy mathematic machinery. Thus, it can be used as a reference by tool developers, teachers, and advanced users.}
}

@inproceedings{EngelsS1999d,
  author = {Gregor Engels AND Stefan Sauer},
  title = {MVC-Based Modeling Support for Embedded Real-Time Systems},
  booktitle = {Proceedings of OMER Workshop, Herrsching, Germany},
  year = {1999},
  editor = {P.Hofmann and A. Schrr},
  pages = {11--14},
  address = {Herrsching, Universit{\"a}t der Bundeswehr M{\"u}nchen, Fakult{\"a}t f{\"u}r Informatik},
  month = {May},
  abstract = {Several software architecture paradigms have been proposed for the development of interactive software systems and applications. Their common idea is the separation of user interface components from application logic. Normally, they are deployed as design patterns or basic frameworks of interactive systems. Deploying these architecture paradigms for multimedia systems or embedded real-time systems, first requires an appropriate adaption to the specific aspects of these application areas. We will compare within this position paper two well-known architecture paradigms and motivate an advanced architecture paradigm applicable to real-time, embedded multimedia systems. In addition, we will discuss that the architecture paradigm should be reflected within the structure of a modeling language.}
}

@inproceedings{Sauer1999c,
  author = {Stefan Sauer AND Gregor Engels},
  title = {OMMMA: An Object-Oriented Approach for Modeling Multimedia Information Systems},
  booktitle = {Proceedings of the workshop on Multimedia Information Systems (MIS 1999), Indian Wells, CA (USA)},
  year = {1999},
  editor = {L. Golubchik and V. J. Tsotras},
  pages = {64--71},
  address = {Indian Wells, California, USA},
  month = {October },
  abstract = {We present an object-oriented approach based on the Unified Modeling Language (UML) for modeling structure and dynamic behavior of a multimedia information system. We extend the Model-View-Controller paradigm for interactive systems towards multimedia and show that aspects of the graphical user interface and time-dynamic behavior ought to be integral parts of a model. This is done in the intention of achieving a coherent model of a multimedia information system. As a result, we present OMMMA-L a UML-based language for the Object-Oriented Modeling of MultiMedia Applications. OMMMA-L deploys class and state diagrams of UML as well as an extended sequence diagram and a newly introduced presentation diagram to adequately specify the visual presentation within a multimedia information system. In addition to explaining the different diagram types, we also define pragmatic rules on how to deploy and combine the various diagrams. Additionally, we relate OMMMA-L to basic ideas of multimedia information systems.}
}

@inproceedings{Sauer1999b,
  author = {Stefan Sauer AND Gregor Engels},
  title = {UML-basierte Modellierung von Multimediaanwendungen},
  booktitle = {Modellierung 1999, Workshop der Gesellschaft f{\"u}r Informatik e. V. (GI), M{\"a}rz 1999 in Karlsruhe},
  year = {1999},
  editor = {J. Desel and K. Pohl and A. Sch{\"u}rr},
  pages = {155--170},
  publisher = {Teubner, Stuttgart},
  address = {Karlsruhe, Germany},
  month = {March},
  abstract = {Der Entwicklungsproze{\ss} von Multimediaanwendungen sollte ebenso wie der herk{\"o}mmlicherSoftwaresysteme eine Analyse und einen Entwurf beinhalten. In dieser Arbeit diskutieren wir,inwiefern die Modellierung der Struktur und des dynamischen Verhaltens einer Multimediaanwendung{\"u}ber die Modellierung herk{\"o}mmlicher Software hinausgeht. Wir zeigen, da{\ss} Aspekte derBenutzungsschnittstelle und das Zeitverhalten integraler Bestandteil der Modellierung sein sollten.Als Ergebnis stellen wir die objektorientierte Modellierungssprache OMMMA-L vor, die auf derUnified Modeling Language (UML) aufbaut. Die Struktur- und Verhaltensdiagramme von UMLwurden analysiert und gem{\"a}{\ss} der Charakteristika von Multimedia adaptiert bzw. erweitert. ImKlassendiagramm werden die Medientypen und die logische Struktur der Anwendung modelliert.Als Verhaltensdiagramme werden spezialisierte Sequenz- und Zustandsdiagramme eingesetzt. Mitdem Layoutdiagramm wird ein neuer Diagrammtyp hinzugef{\"u}gt, der die integrierte und anschaulicheBeschreibung der visuellen Darstellung und interaktiver Benutzereingaben einer Multimediaanwendungerlaubt. Neben der Vorstellung der einzelnen Diagrammtypen geben wir ein aus demMetamodell zu UML abgeleitetes OMMMA-L-Metamodell an, in dem das Zusammenspiel derModellelemente aus den verschiedenen Diagrammen spezifiziert wird.}
}

@inproceedings{Ehrig98,
  author = {Hartmut Ehrig AND Gregor Engels AND Reiko Heckel AND Gabriele Taentzer},
  title = {Classification and Comparison of Modularity Concepts for Graph Transformation Systems},
  booktitle = {Pre-Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT '98), Paderborn (Germany)},
  year = {1998},
  editor = {G. Engels, G. Rozenberg},
  pages = {122--131},
  publisher = {University of Paderborn},
  month = {November},
  abstract = {This paper presents a systematic approach for classifying and comparing modularity concepts that have been proposed for graph transformation systems. The approach is based on the following observation: Modules and module interconnections consist of basic specifications (forming, e.g., a module's body, import, or export interface), and relations between such specifications, like the implementation relation between export and body of a module. Hence, a natural approach for characterizing a module concept is to answer the following three questions: 1. What are the basic specifications? 2. Which relations between specifications are used? 3. How are specifications and relations combined to modules and interconnections? In this paper, these questions are considered in some detail for the following module concepts for graph transformation systems.}
}

@inproceedings{Kolmschlag1998,
  author = {Silvia Kolmschlag AND Gregor Engels},
  title = {Unterst{\"u}tzung der Flexibilit{\"a}t eines Electronic Commerce Systems durch Evolutionstechniken},
  booktitle = {Proceedings of the workshop on "Integration heterogener Softwaresysteme" (satellite event of the GI-Jahrestagung Informatik 1998), Magdeburg (Germany)},
  year = {1998},
  editor = {S. Conrad, W. Hasselbring},
  pages = {13--24},
  publisher = {GI}
}

@inproceedings{Engels1996b,
  author = {Gregor Engels AND Andreas Zamperoni},
  title = {Comprehensive Support for Change: Generic, Multi-dimensional (Software) Engineering Frameworks (position paper)},
  booktitle = {Proceedings of the Workshop on Requirements Engineering in a Changing World (satellite event of the Conference on Advanced Information Systems Engineering (CAISE 1996)), Crete (Greece)},
  year = {1996},
  pages = {42--44},
  month = {May}
}

@inproceedings{Ehrig1996,
  author = {Hartmut Ehrig AND Gregor Engels},
  title = {Pragmatic and Semantic Aspects of a Module Concept for Graph Transformation Systems},
  booktitle = {Selected papers from the 5th International Workshop on Graph Gramars and Their Application to Computer Science, Williamsburg, VA (USA)},
  year = {1996},
  editor = {J. Cuny, H. Ehrig, G. Engels, G. Rozenberg},
  pages = {137--154},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {The paper presents a conceptual framework for a module concept for graph transformation systems from a software engineering as well as from a theoretical point of view. The basic idea is to reuse concepts, which are known within or without the graph grammar field, to structure large specifications. These are the concept of distributed graph transformation systems, the concept of inheritance of specifications, and the import-export-interface concept. All these concepts are presented in a uniform framework based on the syntactical notion of a graph class specification and its semantics given by a graph transformation system. This is the basis for an explicit integration of these concepts and a corresponding specification language, to be discussed in a subsequent paper.},
  volume = {1073}
}

@inproceedings{Groenewegen1996,
  author = {Luuk Groenewegen AND Gregor Engels},
  title = {Reuse of Software Process Fragments is Reuse of Software, too},
  booktitle = {Proceedings of the 10th International Software Process Workshop (ISPW 1996), Ventron (France)},
  year = {1996},
  editor = {B. B{\"o}hm},
  pages = {68},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  abstract = {By means of a special sofnvare process model component we have been successful in specifring somare process model evolution, This component also handles much reuse of software process model fragments. To handle the reuse of the software as it is being produced by a software process, another extra component can be added to the model for that software process. It is argued why this extra component is comparable to the special component for evolution.}
}

@inproceedings{Bunje1996a,
  author = {Tineke de Bunje AND Gregor Engels AND Luuk Groenewegen AND Michael Heus AND Aart Matsinger},
  title = {Towards Measurable Process Models},
  booktitle = {Proceedings of the Workshop on Software Process Technology (EWSPT 1996), Nancy (France)},
  year = {1996},
  editor = {C. Montangero},
  pages = {183--187},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  volume = {1149}
}

@inproceedings{Groenewegen1995,
  author = {Luuk Groenewegen AND Gregor Engels},
  title = {Coordination by Behavioural Views and Communication Patterns},
  booktitle = {Proceedings of the 4th European Workshop on Software Process Technology (EWSPT 1995), Noordwijkerhout (The Netherlands)},
  year = {1995},
  editor = {W. Sch{\"a}fer},
  pages = {189--192},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {April},
  journal = {Software Process Technology},
  series = {LNCS},
  volume = {913}
}

@inproceedings{Engels1995,
  author = {Gregor Engels AND Andy Sch{\"u}rr},
  title = {Encapsulated Hierarchical Graphs, Graph Types, and Meta Types},
  booktitle = {Proceedings of the Joint COMPUGRAPH/SEMAGRAPH Workshop on Graph Rewriting and Computation (SEGRAGRA 1995), Volterra (Italy)},
  year = {1995},
  editor = {A. Corradini, U. Montanari},
  pages = {101-109},
  publisher = {Elsevier},
  address = {Amsterdam, The Netherlands},
  month = {August},
  note = {Joint Compugraph/Semagraph Workshop on Graph Rewriting and Computation},
  abstract = {Currently existing graph grammar-based specification languages have serious problems with supporting any kind of ``specification-in-the-large'' activities. More precisely, they have deficiencies with respect to modeling hierarchical data structures or specifying meta activities like manipulation of graph schemata. Furthermore, already proposed graph grammar module concepts are still too abstract to be useful in practice. Our contribution addresses these problems by introducing a new hierarchical graph data model with an infinite number of schema, meta-schema, etc. layers. It forms the base for a forthcoming concrete modular graph grammar specification language where in addition information hiding aspects like explicit export and import interfaces are expressible.},
  series = {Electronic Notes in Theoretical Computer Science}
}

@inproceedings{EnGr1994socca,
  author = {Gregor Engels AND Luuk Groenewegen},
  title = {Specification of coordinated behaviour by SOCCA},
  booktitle = {Proceedings of the Third European Workshop on Software Process Technology (EWSPT 1994), Villard de Lans (France)},
  year = {1994},
  pages = {128-151},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {February},
  series = {LNCS}
}

@inproceedings{Andries1994,
  author = {Marc Andries AND Gregor Engels},
  title = {Syntax and Semantics of Hybrid Database Languages},
  booktitle = {Proceedings of the International Workshop on Graph Transformations in Computer Science (1993), Dagstuhl (Germany)},
  year = {1994},
  pages = {19--36},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {We present the hybrid query language HQL/EER for an Extended Entity-Relationship model. As its main characteristic, this language allows a user to freely mix graphical and textual formulation of a query. We show how syntax and semantics of this hybrid language are formally defined by means of a slightly extended version of PROGRES, a specification formalism based on programmed and attributed graph rewriting systems.},
  series = {LNCS},
  volume = {776}
}

@inproceedings{Engels1994a,
  author = {Gregor Engels AND Perdita L{\"o}hr},
  title = {Visual Specification of Complex Database Actions},
  booktitle = {Proceedings of the 2nd International East/West Database Workshop, Klagenfurt (Germany)},
  year = {1994},
  editor = {J. Eder, L.A. Kalinichenko},
  pages = {303--314},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {September },
  abstract = {The paper presents an approach to specify in an integrated way by visual, diagrammatic languages the structural and behavioural aspects of database applications. Hereby, well-known extended Entity-Relationship diagrams are employed to specify the structural aspects. The behavioural aspects of a database application are specified by using ViAL (Visual Action Language). ViAL specifications are a special kind of data (or better object) flow diagrams, where so-called elementary actions are used as basic building blocks. These elementary actions are automatically derived from a given EER diagram. They guarantee that after finishing their execution all inherent integrity constraints are fulfilled. The paper explains the features of the language ViAL and gives some illustrating examples.}
}

@inproceedings{Engels1993a,
  author = {Gregor Engels AND Luuk Groenewegen},
  title = {Modular, Visual Specifications of Software Processes},
  booktitle = {Proceedings of the Workshop on Software Process (ISPW 1993), Wadern (Germany)},
  year = {1993},
  editor = {W. Sch{\"a}fer},
  pages = {66--68},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  month = {March}
}

@inproceedings{Engels1992c,
  author = {Gregor Engels AND Perdita L{\"o}hr-Richter},
  title = {CADDY: A Highly Integrated Environment to Support Conceptual Database Design},
  booktitle = {Proceedings of the Fifth International Workshop on Computer-Aided Software Engineering (CASE 1992), Montreal (Canada)},
  year = {1992},
  editor = {G. Forte, N. Madhavji, H.A. M{\"u}ller},
  pages = {19--22},
  publisher = {IEEE Computer Society},
  address = {Washington, DC, USA},
  month = {July },
  abstract = {This experience report describes the development of the CASE environment CADDY Computer-Aided Design of non-traditional Databases 1 which oflers an integrated set of tools for specifying, analyzing, and prototyping a database application on a conceptual level. This environment was designed and implemented during the last four years at Braunschweig Technical University (Germany). The process of developing this environment consisted of a sequence of development steps, where each step corresponded to (at least) one of five main tasks. The intention of this report is to describe these five tasks. At the end, we will critically reflect on the achieved results and solved problems, but also on still open questions of the CADDY environment.}
}

@inproceedings{EngelsG1992b,
  author = {Gregor Engels AND Luuk Groenewegen},
  title = {Specification of Coordinated Behaviour in the Software Development Process},
  booktitle = {Proceedings of the Second European Workshop on Software Process Technology (EWSPT 92), Trondheim, Norway},
  year = {1992},
  editor = {J.C. Derniame},
  pages = {58--60},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  series = {LNCS},
  volume = {635}
}

@inproceedings{Engels1990,
  author = {Gregor Engels},
  title = {Elementary Actions on an Extended Entity-Relationship Database},
  booktitle = {Proceedings of the workshop on Graph Grammars and Their Application to Computer Science (1990), Bremen (Germany)},
  year = {1990},
  editor = {H. Ehrig, H. Kreowski, G. Rozenberg},
  pages = {344--362},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {March},
  note = {Proc. of the 4th Intern. Workshop on Graph Grammars and Their Application to Computer Science},
  abstract = {Semantic data models have been widely studied for the conceptual specification of databases. However, most of these data models are restricted to the description of the static structure of a database. They do not provide means to specify the dynamic behaviour of a database.This paper sketches a language for the specification of actions on databases which have been specified by an Extended Entity-Relationship (EER) schema. These actions are based on so-called elementary actions, which are automatically be derived from the EER schema. So, it can always be guaranteed that these schema dependent elementary actions preserve all inherent integrity constraints.The semantics of the elementary actions is given in two steps: First, it is shown how the semantics of a database schema, i.e., a current database state, can be represented by an attributed graph. Then, the semantics of elementary actions is given by programmed graph replacements.},
  volume = {532}
}

@inproceedings{Engels1988,
  author = {Gregor Engels AND Uwe Hohenstein AND Gunter Saake AND Hans-Dietrich Ehrich},
  title = {Auf dem Weg zu einer integrierten Datenbank-Entwurfsumgebung},
  booktitle = {Proceedings of the GI-Workshop on "Sprachspezifische Programmierumgebungen", Darmstadt (Germany)},
  year = {1988},
  editor = {G. Engels, U. Hohenstein, G. Saake, H.-D. Ehrich},
  pages = {38--51},
  publisher = {G. Snelting},
  month = {April}
}

@inproceedings{EngelsJS1988c,
  author = {Gregor Engels AND Thorsten Janning AND Wilhelm Sch{\"a}fer},
  title = {Die Benutzerschnittstelle einer integrierten Modula-2 Programmentwicklungsumgebung},
  booktitle = {Proceedings of GI-Workshop Sprachspezifische Programmierumgebungen, Darmstadt, Germany},
  year = {1988},
  editor = {G. Snelting},
  month = {April}
}

@inproceedings{Engels1987b,
  author = {Gregor Engels AND Claus Lewerentz AND Wilhelm Sch{\"a}fer},
  title = {Graph Grammar Engineering: A Software Specification Method},
  booktitle = {Proceedings of the 3rd International Workshop on Graph-Grammars and Their Application to Computer Science, Warrenton, VA (USA)},
  year = {1987},
  editor = {H. Ehrig, M. Nagl, G. Rozenberg, A. Rosenfeld},
  pages = {186--201},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Graphs as conceptual data models are accepted and used in a wide range of different problem areas. Giving some examples we outline common aspects for modeling complex structures by graphs. We present a formal frame-work based on graph grammars to specify graph classes and the corresponding graph manipulations. We show that such a specification can be written in a systematic, engineering-like manner. This is achieved by an extension of the known programmed, attributed graph grammars. Node-set operators are introduced to facilitate graph queries. Concepts like abstraction, decomposition, refinement, parameterization, and integration have been adopted from software engineering to yield a comprehensive specification method. This method has successfully been applied to specify the central data structures in a software development environment project},
  volume = {291}
}

@inproceedings{Engels1986a,
  author = {Gregor Engels AND Andrea Sandbrink},
  title = {Experiences with a Hybrid-Interpreter Based on Incremental Compilation Techniques},
  booktitle = {Proceedings of the Workshop on Compiler Compilers and Incremental Compilation Techniques, Bautzen},
  year = {1986},
  pages = {172--184},
  publisher = {Berlin(Ost): Akademie der Wissenschaften der DDR},
  address = {Bautzen},
  journal = {iir - Informatik Informationen},
  volume = {12}
}

@inproceedings{Nagl1983,
  author = {Manfred Nagl AND Gregor Engels AND Rupert Gall AND Wilhelm Sch{\"a}fer},
  title = {Software Specification by Graph Grammars},
  booktitle = {Proceedings of the 2nd International Workshop on Graph-Grammars and Their Application to Computer Science, Osnabr{\"u}ck (Germany)},
  year = {1983},
  editor = {H. Ehrig, M. Nagl, G. Rozenberg},
  pages = {267--287},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {The following paper demonstrates that programmed sequential graph grammars can be used in a systematic proceeding to specify the changes of high level intermediate data structures arising in a programming support environment, in which all tools work in an incremental and syntax-driven mode. In this paper we lay stress upon the way to get the specification rather than on the result of this process. Therefore, we give here some approach to specification engineering using graph grammars. This approach is influenced by the syntactical definition of the underlying programming language or module concept etc. to be supported but also by the idea of the user interface.},
  series = {LNCS},
  volume = {153}
}

@incollection{oswuensc2010,
  author = {Michael Mlynarski AND Baris G{\"u}ldali AND Stephan Wei{\ss}leder AND Gregor Engels},
  title = {Model-Based Testing: Achievements and Future Challenges},
  booktitle = {Advances in Computers},
  year = {2012},
  editor = {Ali Hurson and Atif Memon},
  pages = {1 - 39},
  publisher = {Elsevier},
  month = {September},
  abstract = {Software systems are part of our everyday life and they become more complex day by day. The ever-growing complexity of software and high quality requirements pose tough challenges to quality assurance.The quality of a software system can be measured by software testing. However, if manually done, testing is a time-consuming and error-prone task. Especially test case design and test execution are the most cost-intensive activities in testing. In the previous 20\ years, many automation tools have been introduced for automating test execution by using test scripts. However, the effort for creating and maintaining test scripts remains. Model-based testing (MBT) aims at improving this part by systematizing and automating the test case design. Thereby, test cases or automatable test scripts can be generated systematically from test models.MBT is already known for several years, but it currently gains a great momentum due to advanced tool support and innovative methodological approaches. This chapter aims at giving an overview of MBT and summarizes recent achievements in MBT. Experiences with using the MBT approach are illustrated by reporting on some success stories. Finally, open issues and future research challenges are discussed.}
}

@incollection{oswuensc2010,
  author = {Sebastian Oster AND Andreas W{\"u}bbeke AND Gregor Engels AND Andy Sch{\"u}rr},
  title = {Model-Based Software Product Lines Testing Survey},
  booktitle = {Model-Based Testing For Embedded Systems},
  year = {2010},
  editor = {P. Mosterman, I. Schieferdecker, J. Zander},
  pages = {339--381},
  publisher = {CRC Press},
  month = {July}
}

@incollection{Engels08-4,
  author = {Gregor Engels AND Andreas Hess AND Bernhard Humm AND Oliver Juwig AND Marc Lohmann AND Jan-Peter Richter AND Markus Vo{\ss} AND Johannes Willkomm},
  title = {Anwendungslandschaften serviceorientiert gestalten},
  booktitle = {Handbuch der Softwarearchitektur},
  year = {2008},
  editor = {R. Reussner, W. Hasselbring},
  pages = {151--178},
  organization = {sd\&m},
  publisher = {dpunkt-Verlag},
  month = {March},
  note = {2. Auflage},
  abstract = {Service-orientierte Architekturen (SOA) -- wie mache ich das konkret? Wir stellen mit Quasar Enterprise einen durchg{\"a}ngigen, serviceorientierten Ansatz zur Gestaltung gro{\ss}er Anwendungslandschaften vor. Hierzu verwenden wir ein Architektur-Framework zur Strukturierung der methodischen Schritte und f{\"u}hren ein Dom{\"a}nenmodell zur Pr{\"a}zisierung der Begrifflichkeiten und Entwicklungsartefakte ein. Die dargestellten methodischen Bausteine und Richtlinien beruhen auf langj{\"a}hrigen Erfahrungen in der industriellen Softwareentwicklung bei der sd\&m AG.}
}

@incollection{Eng08,
  author = {Gregor Engels},
  title = {Eintrag "Modellierungssprache"},
  booktitle = {Enzyklop{\"a}die der Wirtschaftsinformatik},
  year = {2008},
  editor = {K. Kurbel, J. Becker, N. Gronau, E. Sinz, L. Suhl},
  publisher = {Oldenbourg Wissenschaftsverlag},
  month = {October}
}

@incollection{Engels2006,
  author = {Gregor Engels AND Marc Lohmann AND Annika Wagner},
  title = {The Web Application Development Process},
  booktitle = {Web Engineering: The Discipline of Systematic Development of Web Applications},
  year = {2006},
  editor = {G. Kappel, B. Pr{\"o}ll, S. Reich, W. Retschitzegger},
  publisher = {Wiley},
  month = {May},
  abstract = {The current situation of ad hoc development of Web applications reminds us of the software development practices of the 1960s, before it was realized that the development of applications required more than programming expertise. This book counteracts this situation by giving a comprehensive, practice-oriented and thorough insight into the new discipline of Web Engineering.The text highlights the need to examine and re-use the body of knowledge found within software engineering. It demonstrates how to use that knowledge within the Web environment, in order to achieve a highly disciplined and methodological means of producing Web-based software, putting emphasize on current practices, experiences and pitfalls. The book demonstrates the distinctions between software engineering and Web engineering, for instance, the shorter lead times that Web engineering has compared to its software counterpart, whilst also demonstrating the rapid prototyping and agile methods of development needed to meet these criteria.The book covers important topics of Web Engineering, including requirements analysis, design, architectures, technologies, test, operation and maintenance; this is complemented by in-depth knowledge about Web project management and process issues as well as important quality aspects of Web applications like usability, performance and security. An overview of Semantic Web concepts points the way to the development of future Web applications. }
}

@incollection{Engels2005a,
  author = {Gregor Engels AND Reiko Heckel AND Alexey Cherchago},
  title = {Flexible Interconnection of Graph Transformation Modules - A Systematic Approach},
  booktitle = {Formal Methods in Software and System Modeling. Essays Dedicated to Hartmut Ehrig on the Occasion of His 60th Birthday},
  year = {2005},
  editor = {H.-J. Kreowski, U. Montanari, F. Orejas, G. Rozenberg, G. Taentzer},
  pages = {38--63},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {Modularization is a well-known concept to structure software systems as well as their specifications. Modules are equipped with export and import interfaces and thus can be connected with other modules requesting or providing certain features. In this paper, we study modules the interfaces of which consist of behavioral specifications given by typed graph transformation systems. We introduce a framework for classifying and systematically defining relations between typed graph transformation systems. The framework comprises a number of standard ingredients, like homomorphisms between type graphs and mappings between sets of graph transformation rules. The framework is applied to develop a novel concept of substitution morphism by separating preconditions and effects in the specification of rules. This substitution morphism is suited to define the semantic relation between export and import interfaces of requesting and providing modules.}
}

@incollection{Engels2005,
  author = {Gregor Engels AND Alexander F{\"o}rster AND Reiko Heckel AND Sebastian Th{\"o}ne},
  title = {Process Modeling using UML},
  booktitle = {Process-Aware Information Systems},
  year = {2005},
  editor = {M. Dumas, W. van der Aalst, A. ter Hofstede},
  pages = {85-117},
  publisher = {Wiley},
  address = {New York, NY},
  abstract = {This chapter provides an introduction to the Unified Modeling Language (UML), a widely adopted object-oriented modeling standard, and shows how the language can be applied to (business) process modeling. As major perspectives of process modeling with UML 2.0, the chapter covers control flow, data objects and object flow, organizational structure, business partner interactions, and system-specific process models. Various types of UML diagrams are presented with a special focus on how these diagrams fit together and complement each other to form a coherent view of a process. Moreover, a running example is used throughout the chapter to illustrate the different facets of a process model.}
}

@incollection{Engels2003,
  author = {Gregor Engels AND Marc Lohmann AND Annika Wagner},
  title = {Entwicklungsprozess von Web-Anwendungen},
  booktitle = {Web Engineering: Systematische Entwicklung von Web-Anwendungen},
  year = {2003},
  editor = {G. Kappel, B. Proell, S. Reich, W. Retschnitzegger},
  pages = {239--264},
  publisher = {dpunkt-Verlag},
  address = {Heidelberg},
  month = {October},
  abstract = {Ist es m{\"o}glich klassische Softwareentwicklungsprozesse f{\"u}r die Entwicklung von Web-Anwendungen zu nutzen? Dazu formulieren wir sechs grundlegende Anforderungen an den Prozess der Entwicklung von Web-Anwendungen. Diese Anforderungen werden zur Evaluation des Rational Unified Process (RUP) und von Extreme Programming (XP) verwendet. Dabei konzentrieren wir uns auf den eigentlichen Prozess, d.h. die Organisation des Ablaufs der Entwicklung, und lassen die zugrunde liegenden Methoden so weit wie m{\"o}glich ausgeklammert. Es zeigt sich,dass keiner der Prozesse in der Lage ist, alle Anforderungen zu erf{\"u}llen. Die St{\"a}rken des RUP liegen in seiner Anpassbarkeit an den Grad der Komplexit{\"a}t der zu entwickelnden Anwendung. Die St{\"a}rken von XP dagegen liegen im Umgang mit kurzen Entwicklungszeiten und sich erst entwickelnden bzw. sich {\"a}ndernden Anforderungen.}
}

@incollection{Engels2002b,
  author = {Gregor Engels AND Ernst-Erich Doberkat},
  title = {Multimedia in der Informatik-Lehre},
  booktitle = {Informatik bewegt. 32. Jahrestagung der Gesellschaft f{\"u}r Informatik, 2002, Lecture Notes in Informatics},
  year = {2002},
  editor = {S. Schubert, B. Reusch, N. Jesse},
  pages = {377--384},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {October},
  abstract = {Neue Medien werden in der universit{\"a}ren Lehre in zunehmendem Ma{\ss}eeingesetzt. Nachdem sich noch vor einigen Jahren nur vereinzelte Pilotprojekte mitdem Thema besch{\"a}ftigt haben, wird inzwischen eine Vielzahl von Projekten {\"o}ffentlichgef{\"o}rdert. Als Beispiel sei das BMBF-F{\"o}rderprogramm Neue Medien inder Hochschullehre genannt.In der Informatik haben nicht zuletzt die hohen Studierendenzahlen dazu beigetragen,multimediale Elemente in der Lehre als ein m{\"o}gliches Mittel zur Bew{\"a}ltigungder hohen Lehrbelastung bei gleichzeitiger Wahrung von Qualit{\"a}t und Vielfalt derLehre anzusehen. Das fachliche Interesse vieler Informatiker am Thema Multimediakommt hinzu.Im Workshop Multimedia in der Informatik-Lehre wird ein {\"U}berblick {\"u}ber gegenw{\"a}rtigeAns{\"a}tze zur Unterst{\"u}tzung der Lehre in der Informatik mit multimedialenMitteln gegeben und es werden Erfahrungen und Konsequenzen diskutiert.}
}

@incollection{Engels2002a,
  author = {Gregor Engels AND Stefan Sauer},
  title = {Object-oriented Modeling of Multimedia Applications},
  booktitle = {Handbook of Software Engineering and Knowledge Engineering},
  year = {2002},
  editor = {S.K. Chang},
  pages = {21--53},
  publisher = {World Scientific Publishing Co. Pte. Ltd.},
  address = {Singapore},
  abstract = {The field of multimedia software engineering is still in an inmature state. Significant research and development has been dedicated towards multimedia services and systems technology such as networking or database systems. Multimedia document formats have been standardized. But when it comes to multimedia application development, the development process is truncated to an implement and test method. Either specialized multimedia authoring systems or multimedia frameworks or toolkits complementing programming languages or system software are directly used for implementation. No preceding modeling phases for requirements specification, analysis, or design of the system to build are enforced. The development of sophisticated multimedia process models and established, usable graphical notations tailored to the specification of multimedia systems is still underway.In order to fill this gap, it is the purpose of this chapter to show current achievements in object-oriented modeling of multimedia applications. Based on an analysis of the state of the art in multimedia application development, we shortly present approaches to object-oriented hypermedia modeling and extensions of the Unified Modeling Language (UML) for hypermedia and interactive systems. The main part of the chapter is dedicated towards a recent approach to the Object-oriented Modeling of MultiMedia Applications (OMMMA).}
}

@incollection{Engels2002,
  author = {Gregor Engels AND Luuk Groenewegen},
  title = {Towards Team-Automata-Driven Object-Oriented Collaborative Work},
  booktitle = {Formal and Natural Computing: Essays Dedicated to Grzegorz Rozenberg},
  year = {2002},
  editor = {W. Brauer, H. Ehring, J. Karhum{\"a}ki, A. Salomaa},
  pages = {257--276},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {The paper studies and compares two different approaches to model communication and cooperation. The approaches are team automata, a well-defined variant of communicating automata, and statecharts, heavily used in object-oriented modelling methods. The comparison yields interesting insights for modelling communication and cooperation. In particular, the differences between action-based, synchronous and state-based, asynchronous communication are elucidated.}
}

@incollection{EngelsGK2000,
  author = {Gregor Engels AND Luuk Groenewegen AND Gerti Kappel},
  title = {Coordinated Collaboration of Objects},
  booktitle = {Proceedings of Advances in Object-Oriented Modeling},
  year = {2000},
  editor = {M.P. Papazoglou, S. Spaccapietra, Z. Tari},
  pages = {307--332},
  publisher = {The MIT Press},
  abstract = {The computer has evolved from the purpose of pure number crunching to supporting the coordinated collaboration between human and/or artificial beings to reach a certain goal. Object-oriented modelling techniques based on the central notions of object interaction and object collaboration should provide the semantic expressivity to model such coordinated collaboration. Based on an investigation of the object-oriented modelling standard UML, however, the weaknesses of the existing modelling concepts are revealed. SOCCA is presented instead, which is an object-oriented specification language supporting the arbitrarily fine-grained synchronisation of processes, i.e., active objects. Based on several examples of the EU rental car system the expressive power of SOCCA is discussed and compared to related approaches.}
}

@incollection{Engels2000b,
  author = {Gregor Engels AND Ralph Depke AND Katharina Mehner},
  title = {Ergebnisse - vergleichende Darstellung},
  booktitle = {Multimedia in der wirtschaftswissenschaftlichen Lehre, Erfahrungsbericht},
  year = {2000},
  editor = {E.-E. Doberkat, G. Engels, M. Grauer, H.L. Grob, U. Kelter, W. Leidhold, V. Nienhaus},
  pages = {277--294},
  publisher = {LIT},
  address = {M{\"u}nster},
  month = {April},
  abstract = {Auf der Grundlage der im vorherigen Kapitel zusammengefa{\ss}ten Beschreibungen derAktivit{\"a}ten an den einzelnen Standorten Bochum, K{\"o}ln, M{\"u}nster und Siegen soll in diesemKapitel versucht werden, die beschriebenen Erfahrungen zu strukturieren und zuvergleichen. Hierbei geht es in erster Linie um eine qualitative Analyse. Es wird also nichtgefragt und bewertet, welche konkret quantitativ me{\ss}baren Ergebnisse erzielt wurden,sondern welcher Standort welche Aktivit{\"a}ten durchgef{\"u}hrt hat, um das gesteckte Ziel zuerreichen. Das Ziel dieser vergleichenden Analyse liegt vor allem in dem Erkenntnisgewinn,welche Aktivit{\"a}ten von welchen Personenkreisen in einer Fakult{\"a}t durchgef{\"u}hrt werdenk{\"o}nnen bzw. sollten, um eine ad{\"a}quate Unterst{\"u}tzung der Lehre durch Multimedia-Technikenzu erzielen.}
}

@incollection{Engels2000a,
  author = {Gregor Engels AND Udo Kelter AND Ralph Depke AND Katharina Mehner},
  title = {Unterst{\"u}tzende Angebote der Softwarebegleitgruppe},
  booktitle = {Multimedia in der wirtschaftswissenschaftlichen Lehre, Erfahrungsbericht},
  year = {2000},
  editor = {E.-E. Doberkat, G. Engels, M. Grauer, H.L. Grob, U. Kelter, W. Leidhold, V. Nienhaus},
  pages = {27--56},
  publisher = {LIT},
  address = {M{\"u}nster},
  month = {April},
  abstract = {In diesem Kapitel sollen das Vorgehensmodell zur Entwicklung von multimedialenLehreinheiten und der Fragebogen zur Erstellung eines deskriptiven Vorgehensmodellsvorgestellt werden. Diese Dokumente sind von der Softwarebegleitgruppe im Projektverlauff{\"u}r die Projektteilnehmer aus den wirtschaftswissenschaftlichen Fakult{\"a}ten erstellt worden.}
}

@incollection{Heckel1999,
  author = {Reiko Heckel AND Gregor Engels AND Hartmut Ehrig AND Gabriele Taentzer},
  title = {A View-based Approach to System Modeling Based on Open Graph Transformation Systems},
  booktitle = {Handbook of Graph Grammars and Computing by Graph Transformations, Volume 2: Applications, Languages and Tools},
  year = {1999},
  editor = {H. Ehrig, G. Engels, H.-J. Kreowski, G. Rozenberg},
  pages = {639--668},
  publisher = {World Scientific},
  address = {Singapore},
  abstract = {The idea of a combined reference model- and view-based specification approach has been proposed recently in the software engineering community. In this chapter we present a specification technique based on open graph transformation systems (in the double-pushout approach) by a new loose semantics for rule-based systems, which allows to model the interaction between different views, and by explicit frame conditions which restrict these interactions to an interface of open types. On this background, formal notions of view and view relation are developed and the behavior of views is described by the loose semantics. Based on the assumption that dependencies between different views are faithfully described by a common reference model, a construction is developed for the automatic integration of views. The views and the reference model are kept consistent manually, which is the task of a model manager. All concepts and results are illustrated at the well-known example of banking system.}
}

@incollection{Heckel1999a,
  author = {Reiko Heckel AND Gregor Engels AND Hartmut Ehrig AND Gabriele Taentzer},
  title = {Classification and Comparison of Module Concepts for Graph Transformation Systems},
  booktitle = {Handbook of Graph Grammars and Computing by Graph Transformations, Volume 2: Applications, Languages and Tools},
  year = {1999},
  editor = {H. Ehrig, G. Engels, H.-J. Kreowski, G. Rozenberg},
  pages = {669--689},
  publisher = {World Scientific},
  address = {Singapore},
  abstract = {In this chapter we use a three-level approach for analyzing module concepts forgraph transformation systems. Based on the observation that module architecturesconsist of basic specications like body or export interface and relations like theimplementation relation between them, or the import relation between a client anda server module, module concepts are characterized by answering the questions1. What are the basic specifications?2. Which relations between specifications are used?3. How are specifications and relations combined to module architectures?These three questions are investigated for five module concepts available in theliterature. As a reference example, a samplemodular specification of resource management in distributed operating systems is presented.}
}

@incollection{Andries1997,
  author = {Gregor Engels AND Jan Rekers AND Marc Andries},
  title = {How to represent a visual specification},
  booktitle = {Visual Language Theory},
  year = {1997},
  editor = {K. Marriott, B. Meyer},
  pages = {241--255},
  publisher = {Springer},
  address = {Berlin/Heidelberg}
}

@incollection{Engels1996,
  author = {Gregor Engels AND Manfred Nagl AND Wilhelm Sch{\"a}fer AND Bernhard Westfechtel},
  title = {Tight Integration on One Document: The Programming Environment},
  booktitle = {Building Tightly Integrated Software Development Environments: The IPSEN Approach},
  year = {1996},
  editor = {M. Nagl},
  pages = {170--177},
  publisher = {Springer},
  address = {Berlin/Heidelberg}
}

@incollection{Ebert1994,
  author = {J{\"u}rgen Ebert AND Gregor Engels},
  title = {Design Representation},
  booktitle = {Encyclopedia of Software Engineering},
  year = {1994},
  editor = {J.J. Marciniak},
  pages = {382-394},
  publisher = {John Wiley \& Sons, Inc.},
  note = {New York,NY (USA)},
  abstract = {This article gives an overview on how to represent the outcome of the software design phase in design documents. The descriptive aspects of the design description languages are stressed. The focus is on sequential systems and the description is arranged according to the main paradigms that are used in indentifying software components. Following a general discussion on how to represent software architectures of large systems, each design paradigm is discussend separately with its basic concepts, its historical background and its main variants. Some multiparadigmatic approaches are discussed, as well which integrate several of the aspects introduced before.}
}

@incollection{Engels1994,
  author = {Gregor Engels AND Luuk Groenewegen},
  title = {SOCCA: Specifications of Coordinated and Cooperative Activities},
  booktitle = {Software Process Modelling and Technology},
  year = {1994},
  editor = {A. Finkelstein, J. Kramer, B.A. Nuseibeh},
  pages = {71--102},
  publisher = {Research Studies Press},
  address = {Taunton}
}

@proceedings{EEKR-2012,
  title = {Graph Transformation - 6th International Conference, ICGT 2012, Bremen, Germany, September 24-29, 2012, Proceedings},
  year = {2012},
  editor = {H. Ehrig, G. Engels, H.-J. Kreowski, G. Rozenberg},
  publisher = {Springer},
  organization = {6th International Conference, ICGT 2012, Bremen, September 24-29, 2012, Proceedings},
  month = {September},
  abstract = {This book constitutes the proceedings of the 6th International Conference on Graph Transformations, ICGT 2012, held in Bremen, Germany, in September 2012.The 30 papers and 3 invited papers presented were carefully reviewed and selected from numerous submissions. The papers are organized in topical sections on behavioural analysis, high-level graph transformation, revisited approaches, general transformation models, structuring and verification, graph transformations in use, (meta-)model evolution and incremental approaches.Content Level » ResearchKeywords » approximated verification - bisimilarity - concurrency - graph theory - parallelismRelated subjects » Software Engineering - Theoretical Computer Science },
  volume = {7562},
  series = {LNCS}
}

@proceedings{ELSSW10,
  title = {Graph Transformations and Model-Driven Engineering - Essays Dedicated to Manfred Nagl on the Occasion of his 65th Birthday},
  year = {2010},
  editor = {G. Engels, C. Lewerentz, W. Sch{\"a}fer, A. Sch{\"u}rr, B. Westfechtel},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  abstract = {This festschrift volume, published in honor of Manfred Nagl on the occasion of his 65th birthday, contains 30 refereed contributions, edited by five of his academic descendants. The types of papers vary significantly, including classic research papers in the style of journal articles, surveys of focused research areas, essays reflecting on certain research topics, and papers summarizing long-term work conducted by Manfred Nagl. The volume is structured in five parts: graph transformations, software architectures and reengineering, process support, embedded systems engineering as well as engineering design applications.},
  volume = {5765},
  series = {LNCS}
}

@proceedings{EKM10,
  title = {Modellierung 2010, Klagenfurt ({\"O}sterreich)},
  year = {2010},
  editor = {Gregor Engels, Dimitris Karagiannis, Heinrich C. Mayr},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  volume = {P-161},
  series = {Lecture Notes in Informatics}
}

@proceedings{ELS09,
  title = {Software Engineering 2010 - Proceedings, Paderborn (Germany)},
  year = {2010},
  editor = {G. Engels, M. Luckey, W. Sch{\"a}fer},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {February},
  volume = {P-159},
  series = {Lecture Notes in Informatics}
}

@proceedings{ELS10,
  title = {Software Engineering 2010 - Workshop Proceedings (inkl. Doktoranden Symposium), Paderborn (Germany)},
  year = {2010},
  editor = {G. Engels, M. Luckey, A. Pretschner, R. Reussner},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {5},
  volume = {P-160},
  series = {Lecture Notes in Informatics}
}

@proceedings{ERMS09,
  title = {Proceedings of Design for Future - 1. Workshop des GI-Arbeitskreises "Langlebige Softwaresysteme (L2S2)"},
  year = {2009},
  editor = {G. Engels, R. Reussner, C. Momm, S. Sauer},
  publisher = {Karlsruhe},
  note = {15.-16. Oktober 2009FZI Forschungszentrum Informatik, Karlsruhe},
  volume = {537},
  series = {CEUR Workshop Proceedings}
}

@proceedings{Engels2007b,
  title = {Proceedings of the 10th International Conference on Model Driven Engineering Languages and Systems (MoDELS 2007), Nashville, TN (USA)},
  year = {2007},
  editor = {Gregor Engels, Bill Opdyke, Douglas C. Schmidt, Frank Weil},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  volume = {4735},
  series = {LNCS}
}

@proceedings{Engels2004,
  title = {Modeling and Development of Multimedia Systems},
  year = {2004},
  editor = {G. Engels, S. Sauer},
  publisher = {World Scientific},
  month = {December},
  note = {(guest editors)},
  volume = {14},
  number = {6},
  series = {Special Issue of the International Journal of Software Engineering and Knowledge Engineering}
}

@proceedings{Engels2004a,
  title = {Proceedings of "DeLFI 2004: Die 2. e-Learning Fachtagung Informatik", Paderborn (Germany)},
  year = {2004},
  editor = {G. Engels, S. Seehusen},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  note = {6.-8. September 2004 in Paderborn},
  number = {P-52},
  series = {Lecture Notes in Informatics}
}

@proceedings{Ehrig2004,
  title = {Proceedings of the 2nd International Conference on Graph Transformations (ICGT 2004), Rome (Italy)},
  year = {2004},
  editor = {H. Ehrig, G. Engels, F. Parisi-Presicce, G. Rozenberg},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {September},
  volume = {3256},
  series = {LNCS}
}

@proceedings{Engels01b,
  title = {Modellierung 2001},
  year = {2001},
  editor = {G. Engels, A. Oberweis, A. Z{\"u}ndorf},
  publisher = {Gesellschaft f{\"u}r Informatik (GI)},
  address = {Bonn},
  month = {March},
  abstract = {Die seit 1998 bestehende Workshop-Reihe Modellierung hat es sich zum Ziel gesetzt, ein Forum f{\"u}r den interdisziplin{\"a}ren Austausch von Ans{\"a}tzen und Erfahrun gen im Bereich der Modellierung zu bieten. Da in den einzelnen Fachdisziplinen unterschiedliche Traditionen und Terminologien in Bezug auf Modellierung bestehen, sind solche disziplin{\"u}bergreifenden Arbeitstreffen besonders n{\"u}tzlich und fruchtbar.Modellierung 2001 bietet daher Wissenschaftlern und Praktikern erneut die Gelegenheit, Gemeinsamkeiten, Defizite und Unterschiede in den verwendeten Mo dellierungsans{\"a}tzen herauszuarbeiten und gegenseitigen Erfahrungsaustausch zu pflegen. Um diesen Anspruch zu unterstreichen, wird es auch w{\"a}hrend der Modellierung 2001 neben den Vortr{\"a}gen viel Raum f{\"u}r Diskussionen geben. },
  volume = {1},
  series = {Lecture Notes in Informatics}
}

@proceedings{Ehrig00,
  title = {Special Issue: Selected Papers of GRATRA 2000},
  year = {2000},
  editor = {H. Ehrig, G. Engels, H.-J. Kreowski, G. Taentzer},
  publisher = {Elsevier},
  address = {Amsterdam, The Netherlands},
  volume = {44},
  number = {2},
  series = {Science of Computer Programming}
}

@proceedings{Engels99-2,
  title = {Informatik '99: Informatik {\"u}berwindet Grenzen. Tagungsband der 29. Jahrestagung der Gesellschaft f{\"u}r Informatik, Paderborn (Germany)},
  year = {1999},
  editor = {G. Engels, K. Beiersd{\"o}rfer, W. Sch{\"a}fer},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {October},
  series = {Informatik aktuell}
}

@proceedings{Engels00-2,
  title = {6th International Workshop on Theory and Applications of Graph Transformations (TAGT '98), Paderborn, Selected Papers},
  year = {1998},
  editor = {G. Engels, H. Ehrig, H.-J. Kreowski, G. Rozenberg},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {November },
  abstract = {This book constitutes the thoroughly refereed post-workshop proceedings of the 6th International Workshop on Theory and Applications of Graph Transformations held in Paderborn, Germany, in November 1998. The 33 revised full papers presented in the book were carefully reviewed and selected from a total of 55 papers presented at the meeting. The book addresses all current aspects in the area. The papers are organized in sections on graph languages, graph theory, categorical approaches, concurrency and distribution, artificial intelligence, visual languages, specification concepts, modularity and refinement, and software engineering. },
  volume = {1764},
  series = {LNCS}
}

@proceedings{Engels98,
  title = {Semi-Formal and Formal Specification Techniques},
  year = {1998},
  editor = {G. Engels, H. Ehrig, F. Orejas, M. Wirsing},
  publisher = {Schloss Dagstuhl, Leibniz Center for Informatics},
  month = {Juli},
  abstract = {During the last 20 years several different formal and semi-formal specification techniques have been successfully developed and used. Applications comprise the specification of simple programs, data types and processes as well as complex hardware and software systems. The variety of specification techniques ranges from formal set theoretical, algebraic, and logic approaches for specifying sequential systems and from Petri-nets, process algebras, automata, and graph grammars for specifying concurrent and distributed behaviors to semi-formal software engineering methods for developing complex systems.Formal and semi-formal approaches have their advantages and disadvantages: the informal diagrammatic methods are easier to understand and to apply but they can be ambiguous. Due to the different nature of the employed diagrams and descriptions it is often difficult to get a comprehensive view of all functional and dynamic properties. On the other hand, the formal approaches are more difficult to learn and require mathematical training. But they provide mathematical rigor for analysis and prototyping of designs. Verification is possible only with formal techniques.Since a few years many researchers and research groups are putting more and more effort in closing this gap by integrating semi-formal and formal specification techniques. Their studies and experiences show the added value of combining semi-formal and formal techniques and at the same time open a whole range of new problems and questions which cannot be asked when studying formalisms in isolation.In this seminar more than 40 scientists came together in 28 talks and two panel discussions to study possibilities and solutions for integrating and validating different formal and semi-formal specification techniques. Similarities and differences of formal and semi-formal specification formalisms as well as possibilities for combining such techniques were discussed. Most talks of this seminar analysed, compared, or integrated at least two such methods.On behalf of all participants the organizers would like to thank the staff of Schloss Dagstuhl for providing an excellent environment to the conference. The support of the TMR programme of the European Community is gratefully acknowledged. Due to this programme it was possible to fund the participation of several young researchers and of three key note speakers. },
  volume = {218},
  series = {Dagstuhl-Seminar-Report}
}

@proceedings{Engels97-2,
  title = {Themenheft: Softwaretechnik},
  year = {1997},
  editor = {G. Engels},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {December },
  note = {(guest editor)},
  volume = {12},
  number = {4},
  series = {Informatik: Forschung und Entwicklung}
}

@proceedings{Engels96,
  title = {Special Issue on Graph Transformations},
  year = {1996},
  editor = {A. Skowron, G. Engels, H. Ehrig, G. Rozenberg},
  publisher = {IOS Press},
  address = {Amsterdam},
  month = {June},
  volume = {26},
  number = {3-4},
  series = {Fundamenta Informaticae}
}

@proceedings{Ehrich94,
  title = {Fundamentals of Object-Oriented Languages, Systems, and Methods},
  year = {1994},
  editor = {H.-D. Ehrich, G. Engels, J. Paredaens, P. Wegner},
  publisher = {Schloss Dagstuhl, Leibniz Center for Informatics},
  month = {August},
  abstract = {During the last decades there has been progress within the object-oriented community in agreeing on what object- orientedness means. The role of object identity, specialization, inheritance, and dynamic binding have been examined. However, a careful look at articles written by people with a theory, programming language, database, and software engineering background shows that the semantical understanding of the same features still differs considerably. A well-known example is the feature of inheritance, which has quite a different meaning for persons from the database comunity with a semantic data model background and persons form the programming language community with a compiling technique background This observation also applies to the literaute on object-oriented software development methods. Here, object -oriented analysis and design methods are often heavily influenced by semantic data modelling consepts- An implemantion of an object-orinted design by an objeckt-oriented progamming language usually causes more difficulties than expected although the "same" object-oriente paradigm is used...},
  volume = {95},
  series = {Dagstuhl-Seminar-Report}
}

@proceedings{Cuny96,
  title = {Graph Gramars and Their Application to Computer Science, 5th International Workshop (1994), Selected Papers},
  year = {1994},
  publisher = {Springer},
  address = {Berlin/Heidelberg},
  month = {November},
  abstract = {This book contains a collection of 37 refereed full papers selected from the contributions presented at the 5th International Workshop on Graph Grammars and Their Applications to Computer Science, held in Williamsburg, Virginia, USA, in November 1994.The book covers the whole spectrum of methods and techniques for the investigation of the structure of graphs and graph transformations. The papers are divided into nine topical sections on rewriting techniques, specification and semantics, software engineering, algorithms and architectures, concurrency, graph languages, pattern and graphics, structure and logic of graphs, and biology.},
  volume = {1073},
  series = {LNCS}
}

@proceedings{Ehrich1989,
  title = {Abstracts des Workshops "Grundlagen von Datenbanken", Volkse (Germany)},
  year = {1989},
  editor = {H.-D. Ehrich, G. Engels, M. Gogolla, G. Saake},
  publisher = {Technische Universit{\"a}t Braunschweig},
  number = {89--02},
  series = {Informatik-Berichte}
}

@techreport{GerthTR10,
  author = {Christian Gerth AND Markus Luckey AND Jochen K{\"u}ster AND Gregor Engels},
  title = {Detection of Semantically Equivalent Fragments for Business Process Model Change Management},
  institution = {IBM Research - Zurich},
  year = {2010},
  type = {IBM Research Report},
  number = {3767},
  month = {February},
  abstract = {Modern business process modeling environments support distributed development by means of model version control, i.e., comparison and merging of two different model versions. This is a challenging task since most modeling languages support an almost arbitrary creation of process models. Thus, in multi-developer environments, process models or parts of them are often syntactically very different but semantically equivalent. Hence, the comparison of business process models must be performed on a semantic level rather then on a syntactic level. For the domain of business process modeling, this problem is yet unsolved.This paper describes an approach that allows the semantic comparison of different business process models using a normal form. For that purpose, the process models are fully automatically translated into process model terms and normalized using a term rewriting system. The resulting normal forms can be efficiently compared. Our approach enables the semantic comparison of business process models ignoring syntactic redundancies.}
}

@techreport{Lohmann2006b,
  author = {Marc Lohmann AND Jan-Peter Richter AND Gregor Engels AND Baris G{\"u}ldali AND Oliver Juwig AND Stefan Sauer},
  title = {Semantische Beschreibung von Enterprise Services -- Eine industrielle Fallstudie},
  institution = {University of Paderborn, s-lab},
  year = {2006},
  type = {s-lab report},
  number = {1},
  month = {May},
  abstract = {Serviceorientierte Architekturen (SOA) erlauben eine schnelle und kosteneffiziente Bereitstellung unterschiedlicher Funktionalit{\"a}ten zur Unterst{\"u}tzung der Gesch{\"a}ftsprozesse eines Unternehmens. Dazu werden fachliche Funktionalit{\"a}ten in Form von Enterprise Services zur Verf{\"u}gung gestellt. Die hohe Zahl von Enterprise Services erfordert eine geeignete semantische Beschreibung zu deren effizienten Verwaltung. Zur semantischen Beschreibung von Enterprise Services sowie zur Formulierung von Suchanfragen ist an der Universit{\"a}t Paderborn die Methode der visuellen Kontrakte entwickelt worden. Dieser Bericht stellt die Ergebnisse einer industriellen Fallstudie zur Evaluation der praktischen Anwendbarkeit visueller Kontrakte im Kontext einer SOA vor.}
}

@techreport{Engels06,
  author = {Gregor Engels AND Jan Hendrik Hausmann AND Marc Lohmann AND Stefan Sauer},
  title = {Teaching UML is Teaching Software Engineering is Teaching Abstraction},
  institution = {Fakult{\"a}t f{\"u}r Elektrotechnik,Informatik und Mathematik, Universit{\"a}t Paderborn},
  year = {2005},
  type = {Technical Report },
  month = {October},
  abstract = {As the Unified Modeling Language (UML) has by now seen widespread and successful use in the software industry and academia alike, it has also found its way into many computer science curricula. An outstanding advantage of teaching UML is that it enables an illustration of many crucial concepts of software engineering, far beyond its concrete notation. Most important among these concepts is that of abstraction. We present a course design which demonstrates the use of UML as a vehicle for teaching such core concepts of software engineering. Multimedia elements and tools help to efficiently convey the course's message to the students. }
}

@techreport{EngelsKG2001d,
  author = {Gregor Engels AND Jochen K{\"u}ster AND Luuk Groenewegen},
  title = {On the Specification and Analysis of Protocols in UML-RT},
  institution = {University of Paderborn, Department of Computer Science},
  year = {2001},
  type = {Technical report},
  number = {01-221 },
  month = {January}
}

@techreport{Depke2000,
  author = {Ralph Depke AND Gregor Engels AND Jochen K{\"u}ster},
  title = {On the Integration of Roles in the UML},
  institution = {University of Paderborn, Department of Computer Science},
  year = {2000},
  type = {Technical report},
  number = {214},
  month = {August },
  abstract = {Conventionally, the state space and behavior of an object is determined when the object is created. Attributes and methods are not allowed to be attached to or retracted from an object during its lifetime. In other words, it is not feasible for an object to change its type dynamically. Furthermore, it is not possible to define several different views on an object allowing to exhibit a specific view to another object and hiding part of its features to a particular object. As a consequence, the concept of an object does not reflect appropriately real-world entities which may change their behavior and exhibit only part of their behavior towards another real-world entity. The concept of a role has been considered as an appropriate step forward to solving these kinds of problems. In this paper, we examine the concept of roles and elaborate a proposal for the integration of a clear concept of roles in the UML.}
}

@techreport{Engels1999f,
  author = {Gregor Engels AND Ray Dassen AND Luuk Groenewegen AND Ida G. Sprinkhuizen-Kuyper AND Pieter Koopman AND Pieter Jan t'Hoen},
  title = {A Formalisation of SOCCA using Z, part 1: The Type Level Concepts},
  institution = {Leiden Institute of Advanced Computer Science},
  year = {1999},
  type = {Technical report},
  number = {1999-03},
  abstract = {This document starts the formalisation of the modelling language of the SOCCA OO method in the formal specification language Z. It captures the `static' aspects of SOCCA, i.e. the meaning of SOCCA language elements at the type level, rather than `dynamic' aspects (dealing with the instance level (objects in execution)). It is restricted to core SOCCA; proposed extensions are not formalised.}
}

@techreport{Engels1999e,
  author = {Gregor Engels AND Pieter Jan t'Hoen AND Ray Dassen AND Luuk Groenewegen AND Ida G. Sprinkhuizen-Kuyper AND Pieter Koopman},
  title = {SOCCA Extended with UML like Packages},
  institution = {Leiden Institute of Advanced Computer Science},
  year = {1999},
  type = {Technical report},
  number = {99-06},
  month = {September}
}

@techreport{Engels1999a,
  author = {Gregor Engels AND Roland H{\"u}cking AND Stefan Sauer AND Annika Wagner},
  title = {UML Collaboration Diagrams and Their Transformation to Java},
  institution = {University of Paderborn, Department of Computer Science},
  year = {1999},
  type = {Technical report},
  number = {99-208},
  month = {June},
  note = {Extended version of UML'99. },
  abstract = {UML provides a variety of diagram types for specifying boththe structure and the behavior of a system. During the developmentprocess, models specified by use of these diagram types have to be transformedinto corresponding code. In the past, mainly class diagrams andstate diagrams have been considered for an automatic code generation.In this paper, we focus on collaboration diagrams. As an important prerequisitefor a consistent transformation into Java code, we first providemethodical guidelines on how to deploy collaboration diagrams to modelfunctional behavior. This understanding yields a refined meta model andforms the base for the definition of a transformation algorithm. The automaticallygenerated Java code fragments build a substantial part ofthe functionality and prevent the loss of important information duringthe transition from a model to its implementation.}
}

@techreport{EngelsK1998,
  author = {Gregor Engels AND Silvia Kolmschlag},
  title = {Electronic Commerce Systeme als Anwendungsbeispiel f{\"u}r Evolutionstechniken},
  institution = {University of Paderborn, C-LAB},
  year = {1998},
  type = {C-LAB report},
  number = {06/98}
}

@techreport{Busatto1996,
  author = {Giorgio Busatto AND Gregor Engels},
  title = {Definition of an Encapsulated Hierarchical Graph Data Model: Static Aspects, Part 1.},
  institution = {Vakgroep Informatica, Rijksuniversiteit Leiden},
  year = {1996},
  type = {Technical report},
  number = {96-38},
  month = {December},
  abstract = {Graph grammars have been successfully used as a formalism for the specification of realistic problems but, as far as specification-in-the-large activities are concerned, they still have some deficiencies. In particular, most of them only support the use of flat graphs, whereas for certain applications hierarchical graphs would be a more suitable modelling tool. Furthermore, there is still the need for a graph grammar module concept that allows to split large specifications into smaller sub-specifications. We want to address this problem by applying object-oriented concepts to develop a hierarchical graph data model that supports a suitable module concept for graph grammars. In this paper, we present the first step in the definition of our encapsulated hierarchical graph (EHG) data model. We introduce the notion of EHG that supports complex nodes (i.e. nodes with an encapsulated graph as their content), edges, encapsulated graphs (i.e. graphs that support importing and exporting of nodes and edges), hierarchical structuring of complex nodes (through a node-subnode relationship), and appropriate conditions for exporting elements of a node along a hierarchy of nodes.}
}

@techreport{Andries1996a,
  author = {Marc Andries AND Gregor Engels AND Annegret Habel AND Berthold Hoffmann AND Hans-J{\"o}rg Kreowski AND Sabine Kuske AND Detlef Plump AND Andy Sch{\"u}rr AND Gabriele Taentzer},
  title = {Graph Transformation for Specification and Programming},
  institution = {University of Bremen, Department of Mathematics and Computer Science},
  year = {1996},
  type = {Technical report},
  number = {7/96},
  abstract = {The framework of graph transformation combines the potentials and advantages of both, graphs and rules, into a single computational paradigm. In this paper we survey recent developments in applying graph transformation as a rule-based framework for the specification and development of systems, languages, and tools. After presenting the basic features of graph transformation, we discuss a spectrum of applications including the evaluation of functional expressions, the specification of an interactive graphical tool, an example specification for abstract data types, and the definition of a visual database query language. The case studies indicate the need for a graph transformation language that provides suitable structuring principles and is independent of a particular graph transformation approach. To this end, we sketch the basic features of the new graph- and rule-centered language Grace, currently under development, that permits systematic and structured specification and programming based on graph transformation.}
}

@techreport{Engels1996c,
  author = {Gregor Engels AND Luuk Groenewegen AND Gerti Kappel},
  title = {Object-oriented Specification of Coordinated Collaboration},
  institution = {Vakgroep Informatica, Rijksuniversiteit Leiden},
  year = {1996},
  type = {Technical report},
  month = {August}
}

@techreport{Engels1995a,
  author = {Gregor Engels AND Andy Sch{\"u}rr},
  title = {Encapsulated Hierarchical Graphs, Graph Types, and Meta Types},
  institution = {Vakgroep Informatica, Rijksuniversiteit Leiden},
  year = {1995},
  type = {Technical report},
  number = {95-21},
  month = {July},
  abstract = {Currently existing graph grammar-based specification languages have serious problems with supporting any kind of "specification-in-the-large" activities. More precisely they have deficiences with respect to modeling hierarchical data structures or specifying meta activities like manipulation of graph schemata. Furthermore already proposed graph grammar module concepts are still too abstract to be useful in practice. Our contribution addresses these problems by introducing a new hierarchical graph data model with an infinite number of schema, meta-schema, etc. layers. It forms the base for a forthcoming concrete modular graph grammar specification language where in addition information hiding aspects like explicit export and import interfaces are expressible.}
}

@techreport{EbeEng1995,
  author = {J{\"u}rgen Ebert AND Gregor Engels},
  title = {Specialization of Object Life Cycle Definitions},
  institution = {University of Koblenz-Landau},
  year = {1995},
  type = {Fachbericht Informatik},
  number = {19/95},
  month = {December},
  note = {Koblenz},
  abstract = {Several object-oriented modeling approaches propose to describe the dynamic behaviour of objects by state transition diagrams. None of them provides precise rules or conditions for the interrelation between the behaviour description of classes and those of their subclasses. In this paper, we discuss this interrelation in detail. It turns out that one has to distinguish between the observable and the invocable behaviour of objects and that different compatibility requirements between the diagrams exist depending on the type of behaviour.}
}

@techreport{Ebert1994b,
  author = {J{\"u}rgen Ebert AND Gregor Engels},
  title = {Observable or Invocable Behaviour - You Have to Choose},
  institution = {Vakgroep Informatica, Rijksuniversiteit Leiden},
  year = {1994},
  type = {Technical report},
  number = {94-38},
  month = {December},
  abstract = {Several object-oriented modeling approaches propose to describe the dynamic behaviour of objects by state transition diagrams. None of them provide precise rules or conditions for the interrelation between the behaviour description of classes and those of their subclasses. In this paper, we discuss this interrelation in detail. It turns out that one has to distinguish between the observable and the invocable behaviour of objects and that different compatibility requirements between the diagrams exist depending on the type of behaviour.}
}

@techreport{Andries1993,
  author = {Marc Andries AND Gregor Engels},
  title = {A Hybrid Query Language for the Extended Entity Relationship Model},
  institution = {Vakgroep Informatica, Rijksuniversiteit Leiden},
  year = {1993},
  type = {Technical Report},
  number = {93-15},
  abstract = {We present the hybrid query language HQL/EER for an Extended Entity-Relationship model. As its main characteristic, this language allows a user to freely mix graphical and textual formulation of a query. We demonstrate the user-friendliness of this query language by means of examples, and show how syntax and semantics of this language are formally defined using programmed graph rewriting systems. Although we present the language in the context of the EER model, the concept of hybrid languages is applicable in the context of other database models as well. }
}

@techreport{Engels93,
  author = {Gregor Engels AND Grzegorz Rozenberg},
  title = {Abstracts COMPUGRAPH II Workshop},
  institution = {Vakgroep Informatica, Rijksuniversiteit Leiden},
  year = {1993},
  type = {Technical Report},
  number = {93-26},
  month = {September }
}

@techreport{Ehrig1993,
  author = {Hartmut Ehrig AND Gregor Engels},
  title = {Towards a Module Concept for Graph Transformation Systems},
  institution = {Vakgroep Informatica, Rijksuniversiteit Leiden},
  year = {1993},
  type = {Technical report},
  number = {93-34},
  month = {October}
}

@techreport{Engels1992e,
  author = {Gregor Engels},
  title = {Visual Specifications of Conceptual Database Schemata (Abstract)},
  institution = {Leiden University},
  year = {1992},
  type = {Dagstuhl-Seminar-Report: Foundation of Information Systems Specification and Design},
  month = {M{\"a}rz }
}

@techreport{Loehr-Richter1991,
  author = {Perdita L{\"o}hr-Richter AND Gregor Engels},
  title = {Incremental Design of Conceptual Database Schemata with CADDY},
  institution = {Vakgroep Informatica, Rijksuniversiteit Leiden},
  year = {1991},
  type = {Technical report},
  number = {91-23},
  address = {Leiden University, P.O. Box 9500, 2300 RA Leiden, The Netherlands},
  month = {December}
}

@techreport{Engels1998,
  author = {Gregor Engels},
  title = {Benutzerschnittstelle und Architektur der integrierten Datenbankentwurfsumgebung CADDY (Kurzfassung)},
  institution = {TU Braunschweig},
  year = {1989},
  type = {Forschungsbericht},
  number = {89-02},
  month = {Mai}
}

@techreport{Ebert1988,
  author = {J{\"u}rgen Ebert AND Gregor Engels},
  title = {Ein Konzept zur Beschreibung von Software-Architekturen},
  institution = {EWH Koblenz},
  year = {1988},
  type = {Fachberichte Informatik},
  number = {11/88}
}

@techreport{Engels1981,
  author = {Gregor Engels AND Udo Pletat AND Hans-Dietrich Ehrich},
  title = {Handling Errors and Exceptions in the Algebraic Specifications of Data Types},
  institution = {University of Osnabr{\"u}ck},
  year = {1981},
  type = {Technical report},
  number = {OSM-I-3}
}

@techreport{Pletat1981,
  author = {Udo Pletat AND Gregor Engels AND Hans-Dietrich Ehrich},
  title = {Operational Semantics of Algebraic Specifications with Conditional Equations},
  institution = {University of Dortmund, Department of Computer Science},
  year = {1981},
  type = {Technical report},
  number = {118}
}

@booklet{Engels08-3,
  title = {Principles of Service-Oriented Architectures (SOA)},
  author = {Gregor Engels},
  howpublished = {Tutorial at the 30th International Conference on Software Engineering (ICSE '08), Leipzig (Germany)},
  month = {May},
  year = {2008},
  abstract = {Service-oriented architectures (SOA) are promoted as the final answer to the long standing demand to bridge the gap between business needs and IT-solutions. Like object-orientation has been advocated as the overall structuring principle in the 90s, service-orientation is nowadays discussed as the magic bullet to align business requirements with software applications.As it is typical for any hype approach, a commonly agreed understanding of the basic principles and notions for service-oriented concepts is still missing. This leads often to misunderstandings and communication problems in IT-projects and, thus, jeopardizes the success of migration projects where existing architectures are advanced towards service-oriented architectures.The tutorial aims at clarifying the understanding of basic principles, notions, languages as well as methods of a service-oriented approach. It lays the foundation for Tutorial T11, which will show how SOA is used in practice to achieve enterprise integration. All introduced concepts are related to existing knowledge on software architectures, architectural styles, and architecture frameworks. Presented methodical guidelines have been derived from successful industrial IT-projects and are part of Quasar Enterprise, the service-oriented development approach of sd\&m AG, Munich (Germany).The tutorial is intended for industrial as well as academic people who are interested in a better understanding of basic principles and notions of service-oriented architectures, in order to judge benefits and risks of following a service-oriented approach.}
}

@booklet{Engels,
  title = {Object-Oriented System Development - From Analysis to Implementation},
  author = {Gregor Engels AND Gerti Kappel},
  howpublished = {Tutorials at the European Software Engineering Conference (ESEC '93), Garmisch-Partenkirchen (Germany), the International Conference on Database and Expert Systems Applications (DEXA '93), Prague (Czech Republic), and the International Conference on Data Engineering (ICDE '94), Houston, TX (USA)},
  year = {1993},
  abstract = {Object-oriented system development is widely recognized as improvingproductivity and reducing system maintenance costs.Since the late eighties an ever growing number of methods covering (part of)object-oriented analysis, design and implementation has been proposed.Independent from any concrete object-oriented method, however, there are threeimportant questions, equally relevant to practitioners and researchers.Firstly, what are the concepts, tasks, and results of analysis, design andimplementation in an object-oriented framework to system development and how dothey relate to each other?Secondly, how does object-oriented system development compare to traditionalapproaches?And thirdly, what are the pitfalls of object-oriented system development andhow to cope with them? The tutorial will provide answers to all three questionsin concert.}
}

@booklet{Engels92,
  title = {Query Languages for the Extended ER Model},
  author = {Gregor Engels},
  howpublished = {Tutorial at the workshop "SION Ph.D. Students Information Systems", Mierlo (The Netherlands)},
  month = {June},
  year = {1992}
}

@booklet{Ebert91,
  title = {Design Description Methods},
  author = {J{\"u}rgen Ebert AND Gregor Engels},
  howpublished = {Tutorial at the European Conference on Software Engineering (ESEC '91), Milano (Italy)},
  month = {October},
  year = {1991}
}

@phdthesis{Engels1986,
  author = {Gregor Engels},
  title = {Graphen als zentrale Datenstrukturen in einer Software-Entwicklungsumgebung},
  school = {University of Osnabr{\"u}ck},
  year = {1986},
  month = {March},
  note = {VDI-Fortschritt-Berichte Nr. 62, Dsseldorf: VDI-Verlag 1986Fortschritt-Berichte VDI., Reihe 10,, Angewandte Informatik ;, Nr. 62}
}

@mastersthesis{Engels1980,
  author = {Gregor Engels AND Udo Pletat},
  title = {Analyse von Regelschemata f{\"u}r Unterbaum-Ersetzungssysteme},
  school = {Universit{\"a}t Dortmund, Abt. Informatik},
  year = {1980},
  month = {M{\"a}rz},
  type = {Diploma Thesis}
}

@misc{EngArchi08,
  author = {Arndt Bode AND Manfred Broy AND Uwe Dumslaff AND Gregor Engels},
  title = {Architektur \& Management im Gro{\ss}en meistern},
  howpublished = {Editorial of "Informatik-Spektrum" (special issue "Management gro{\ss}er Systeme"), vol. 31, no. 6. Springer (Berlin/Heidelberg)},
  year = {2008},
  journal = {Informatik-Spektrum}
}

@misc{Doberkat,
  author = {Ernst-Erich Doberkat AND Gregor Engels AND Jan Hendrik Hausmann AND Marc Lohmann AND Christof Veltmann},
  title = {Anforderungen an eine eLearning-Plattform -Innovation und Integration},
  howpublished = {Study for the Ministry of Science and Research, Northrhine-Westfalia, Germany},
  month = {April},
  year = {2002}
}

@misc{Engels1994c,
  author = {Gregor Engels},
  title = {Coordination Constraints (Abstract)},
  howpublished = {In H.-D. Ehrich, G. Engels, J. Paredaens, P. Wegner (eds.): Fundamentals of Object-Oriented Languages, Systems, and Methods- Dagstuhl-Seminar-Report 95},
  month = {August},
  year = {1994},
  abstract = {Nowadays object-oriented analysis and design methods propose to split the specification of a system into several parts, where each part describes a certain perspective. We follow this line and present the object-oirented specification language SOCCA (Specification of Coordinated and Cooperative Activities). A SOCCA specification consists of* a class diagram to describe the structural part of objects and their interrelations with other objects,* state transition diagrams to describe the external behavior ("life cycle") of objects,* an interaction diagram to describe the "uses" relationschip between classes, and* (once more) state trasition diagrams to describe the internal behavior ("realization") of operations.In addition to most of the existing appproaches, we also model the coordination of object behavior explicitly. This is done by splitting the internal behavior description into subdiagrams and by controlling the transition from one subbehavior to another by coordination constraints added to the external behavior description of objects. },
  journal = {Fundamentals of Object-Oriented Languages, Systems, and Methods}
}

@misc{Engels1992d,
  author = {Gregor Engels},
  title = {Graphs as Central Data Structures in a Database Design Environment (Abstract)},
  howpublished = {In P. Klint, T. Reps, G. Snelting (eds.): Programming Environments. Dagstuhl-Seminar-Report 34},
  month = {March},
  year = {1992},
  abstract = {The talk illustrates that graphs are a well-suited data structure to be used for the modelling, i.e., external representation, as well as for the internal representation of database schemas.We present the database design environment CADDY (Computer-Aided conceptual Design of non-traditional Databases) which offers an integrated tool set for editing, and prototyping a conceptual database schema. The theoretical background is given by a semantically well-defined data model which enables the specification of the static structure of an appliction area by an Extended Entity-Relationship diagram and the specification of the dynamic behaviour by temporal integrity constraints and extended data flow graphs. The tool set of CADDY comprises language-sensitive editors for all these specification paradigms and prototyping tools like a query interpreter or a graphical database browser to join experiences with partly developed coneptual database schemata.All developed documents within CADDY are internally represented by attributed abstract syntax graphs. These are extensions of abstract syntax trees, where in addition to context-free interrelations also context-sensitive interrelations are expressed by nodes and edges. The classes of these syntax graphs are specified by an operational specification approach which is based on programmed graph representation systems. These graph grammar specifications serve as guideline for an efficient implementation of all CADDY-tools.},
  journal = {Programming Environments}
}

@misc{Engels1992b,
  author = {Gregor Engels},
  title = {Schakelschema's voor Softwaresystemen},
  howpublished = {Reprint Inaugurale Rede, Rijksuniversit{\"a}t Leiden},
  month = {September},
  year = {1992}
}