@article{7406,
  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).}},
  author       = {{Andries, Marc and Engels, Gregor}},
  journal      = {{Journal of Visual Languages and Computing}},
  number       = {{3}},
  pages        = {{321--352}},
  title        = {{{A Hybrid Query Language for the Extended Entity Relationship Model}}},
  doi          = {{http://dx.doi.org/10.1006/jvlc.1996.0017}},
  volume       = {{7}},
  year         = {{1996}},
}

@inbook{7514,
  author       = {{Engels, Gregor and Nagl, Manfred and Schäfer, Wilhelm and Westfechtel, Bernhard}},
  booktitle    = {{Building Tightly Integrated Software Development Environments: The IPSEN Approach}},
  pages        = {{170--177}},
  publisher    = {{Springer}},
  title        = {{{Tight Integration on One Document: The Programming Environment}}},
  volume       = {{1170}},
  year         = {{1996}},
}

@inproceedings{7831,
  abstract     = {{We present a combination of recent extensions to single-pushout graph transformations, as there are attribution, application conditions and amalgamated graph transformations and add a simple transaction concept on top of this formalism. Thereby, we provide the formal basis for several examples, where these concepts are used in combination.}},
  author       = {{Heckel, Reiko and Müller, Jürgen and Taentzer, Gabriele and Wagner, Annika}},
  booktitle    = {{Proceedings of the Colloquium on Graph Transformation and its Application in Computer Science}},
  number       = {{B-19}},
  publisher    = {{Universitat de les Illes Balears}},
  title        = {{{Attributed Graph Transformations with Controlled Application of Rules}}},
  year         = {{1995}},
}

@inproceedings{7832,
  author       = {{Thoben, Wilfried and Appelrath, Hans-Jürgen and Sauer, Stefan}},
  booktitle    = {{Proceedings of the 18th Annual Conference of the Gesellschaft für Klassifikation, Oldenburg (Germany)}},
  pages        = {{412--419}},
  publisher    = {{Springer}},
  title        = {{{Record Linkage of Anonymous Data by Control Numbers}}},
  year         = {{1995}},
}

@inproceedings{7833,
  abstract     = {{Single pushout graph transformations at injective matches are extended by negative application conditions. It is shown, how right-sided application conditions can be transformed into equivalent left-sided ones. Based on this result, conditional derived rules are introduced and a theorem, similiar to the double pushout embedding theorem is shown. Finally, three variants of contextual application conditions are discussed with respect to their expressive power and expected results.}},
  author       = {{Heckel, Reiko}},
  booktitle    = {{Proceedings of the Colloquium on Graph Transformation and its Application in Computer Science}},
  number       = {{B-19}},
  publisher    = {{Universitat de les Illes Balears}},
  title        = {{{Embedding of Conditional Graph Transformations}}},
  year         = {{1995}},
}

@techreport{8194,
  author       = {{Conrad, Mirko and Gajewsky, Magdalena and Holl-Biniasz, Rainer and Rudolf, Michael and Demuth, Jochen and Weber, Stephan and Heckel, Reiko and Müller, Jürgen and Taentzer, Gabriele and Wagner, Annika}},
  title        = {{{Graphische Spezifikation ausgewählter Teile von AGG - einem algebraischen Graphgrammatiksystem}}},
  year         = {{1995}},
}

@techreport{8195,
  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.}},
  author       = {{Ebert, Jürgen and Engels, Gregor}},
  publisher    = {{University of Koblenz-Landau}},
  title        = {{{Specialization of Object Life Cycle Definitions}}},
  year         = {{1995}},
}

@techreport{8196,
  author       = {{Engels, Gregor and Schürr, Andy}},
  publisher    = {{Vakgroep Informatica, Rijksuniversiteit Leiden}},
  title        = {{{Encapsulated Hierarchical Graphs, Graph Types, and Meta Types}}},
  year         = {{1995}},
}

@inproceedings{8266,
  author       = {{Groenewegen, Luuk and Engels, Gregor}},
  booktitle    = {{Proceedings of the 4th European Workshop on Software Process Technology (EWSPT 1995), Noordwijkerhout (The Netherlands)}},
  pages        = {{189--192}},
  publisher    = {{Springer}},
  title        = {{{Coordination by Behavioural Views and Communication Patterns}}},
  doi          = {{http://dx.doi.org/10.1007/3-540-59205-9_56}},
  volume       = {{913}},
  year         = {{1995}},
}

@inproceedings{8267,
  abstract     = {{Based on a categorical semantics that has been developed for typed graph grammars we uses colimits (pushouts) to model composition and (reverse) graph grammar morphisms to describe refinements of typed graph grammars. Composition of graph grammars w.r.t. common subgrammars is shown to be compatible with the semantics, i.e. the semantics of the composed grammar is obtained as the composition of the semantics of the component grammars. Moreover, the structure of a composed grammar is preserved during a refinement step in the sense that compatible refinements of the components induce a refinement of the composition. The concepts and results are illustrated by an example.}},
  author       = {{Corradini, Andrea and Heckel, Reiko}},
  booktitle    = {{Proceedings of the Joint COMPUGRAPH/SEMAGRAPH Workshop on Graph Rewriting and Computation (SEGRAGRA 1995), Volterra (Italy)}},
  pages        = {{46--55}},
  publisher    = {{Elsevier}},
  title        = {{{A Compositional Approach to Structuring and Refinement of Typed Graph Grammars}}},
  volume       = {{2}},
  year         = {{1995}},
}

@inproceedings{8268,
  abstract     = {{The overall aim of this paper is a proposal how to bridge the gap between formal specification techniques developed in research projects and semi--formal or informal specifications used in industrial practice. The main idea to overcome these problems is to develop graphical support for formal methods in order to increase acceptance by practitioners and to provide means for integration of formal and semi--formal methods. More specifically suitable concepts will be developed to combine algebraic specifications, Petri Nets, and Graph Grammars with each other and with distinguished graphical components to be used by industrial partners.}},
  author       = {{Bardohl, Bernhard and Bardohl, Roswitha and Castro, Paulo and Ehrig, Hartmut and Heckel, Reiko and Ribeiro, Leila and Nunes, Daltro and Martini, Alfio}},
  booktitle    = {{Proceedings of the 3rd German-Brazilian Workshop on Information Technology (1995), Berlin (Germany)}},
  publisher    = {{Forschungszentrum Jülich GmbH}},
  title        = {{{GRAPHIT: Graphical Support and Integration of Formal and Semiformal Methods for Software Specification and Development}}},
  volume       = {{26}},
  year         = {{1995}},
}

@inproceedings{8269,
  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.}},
  author       = {{Engels, Gregor and Schürr, Andy}},
  booktitle    = {{Proceedings of the Joint COMPUGRAPH/SEMAGRAPH Workshop on Graph Rewriting and Computation (SEGRAGRA 1995), Volterra (Italy)}},
  pages        = {{101--109}},
  publisher    = {{Elsevier}},
  title        = {{{Encapsulated Hierarchical Graphs, Graph Types, and Meta Types}}},
  doi          = {{http://dx.doi.org/10.1016/S1571-0661(05)80186-0}},
  year         = {{1995}},
}

@inproceedings{8270,
  author       = {{Heckel, Reiko and Wagner, Annika}},
  booktitle    = {{Proceedings of the Joint COMPUGRAPH/SEMAGRAPH Workshop on Graph Rewriting and Computation (SEGRAGRA 1995), Volterra (Italy)}},
  pages        = {{118--126}},
  publisher    = {{Elsevier}},
  title        = {{{Ensuring Consistency of Conditional Graph Grammars - A constructive Approach}}},
  doi          = {{http://dx.doi.org/10.1016/S1571-0661(05)80188-4}},
  volume       = {{2}},
  year         = {{1995}},
}

@proceedings{7797,
  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...}},
  editor       = {{Ehrich, Hans-Dietrich and Engels, Gregor and Paredaens, J. and Wegner, Jan}},
  publisher    = {{Schloss Dagstuhl, Leibniz Center for Informatics}},
  title        = {{{Fundamentals of Object-Oriented Languages, Systems, and Methods}}},
  volume       = {{95}},
  year         = {{1994}},
}

@proceedings{7798,
  editor       = {{Cuny, Janice and Ehrig, Hartmut and Engels, Gregor and Rozenberg, Grzegorz}},
  publisher    = {{Springer}},
  title        = {{{Graph Gramars and Their Application to Computer Science, 5th International Workshop (1994), Selected Papers}}},
  doi          = {{http://dx.doi.org/10.1007/3-540-61228-9}},
  volume       = {{1073}},
  year         = {{1994}},
}

@inproceedings{7827,
  abstract     = {{Die Pilotphase 1993/ 94 zum Aufbau eines Niedersächsischen Krebsregister untersucht das im Entwurf des Bundeskrebsregistergesetzes vorgesehen Modell für ein bevölkerungsbezogenes Krebsregister. Darin werden die Krebsmeldungen in einer Vertrauensstelle erfaßt und die personenidentifizierenden Daten vor der Übermittlung an die Registerstelle anonymisiert, wo sie dann zu einem bevölkerungsbezogenen Krebsregister verdichtet und epidemiologischer Forschung zur Verfügung gestellt werden ([1], [2], [3]). Dieses sogenannte „Michaelis“-Modell erlaubt eine bevölkerungsbezogene Registrierung von Krebsfällen unter Berücksichtigung datenschutzrechtlicher Aspekte („Informationelles Selbstbestimmungsrecht“) der einzelnen Betroffenen. In vier Teilprojekten werden dabei in der Modellregion Weser-Ems die Integration krebsregistrierender Einrichtungen, die Chiffrierung/ Dechiffrierung von Krebsmeldungen, der Abgleich anonymisierter Meldungen in der Registerstelle und die Entwicklung eines epidemiologischen Informationssystem betrachtet ([4], [5]).}},
  author       = {{Thoben, Wilfried and Appelrath, Hans-Jürgen and Rettig, Jens and Sauer, Stefan}},
  booktitle    = {{Proceedings of the conference on Medizin und Information, Biometrie und Epidemiologie (GMDS 1994), Dresden (Germany)}},
  pages        = {{88--90}},
  publisher    = {{MMV Medizin Verlag}},
  title        = {{{Berücksichtigung von Datenschutzaspekten in einem bevölkerungsbezogenen Krebsregister}}},
  year         = {{1994}},
}

@inproceedings{7828,
  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.}},
  author       = {{Ebert, Jürgen and Engels, Gregor}},
  booktitle    = {{Proceedings of the International Symposium on Object-Oriented Methodologies and Systems (ISOOMS 1994), Palermo (Italy)}},
  pages        = {{142--157}},
  publisher    = {{Springer}},
  title        = {{{Structural and Behavioural Views on OMT-Classes}}},
  volume       = {{858}},
  year         = {{1994}},
}

@inproceedings{7829,
  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.}},
  author       = {{Engels, Gregor and Kappel, Gerti}},
  booktitle    = {{Proceedings of the IFIP 13th World Computer Congress on Information Processing, Hamburg (Germany)}},
  pages        = {{434--441}},
  publisher    = {{Elsevier}},
  title        = {{{Object-Oriented System Development: Will the New Approach Solve Old Problems?}}},
  volume       = {{3}},
  year         = {{1994}},
}

@inproceedings{7830,
  author       = {{Engels, Gregor and Ehrig, Hartmut}},
  booktitle    = {{Proceedings Colloquium on Graph Transformation and its Application in Computer Science}},
  publisher    = {{Universitat de les Illes Balears, Departament de Ci}},
  title        = {{{Towards a Module Concept for Graph Transformation Systems: The Software Engineering Perspective}}},
  volume       = {{B-19}},
  year         = {{1994}},
}

@techreport{8193,
  author       = {{Ebert, Jürgen and Engels, Gregor}},
  publisher    = {{Vakgroep Informatica, Rijksuniversiteit Leiden}},
  title        = {{{Observable or Invocable Behaviour - You Have to Choose}}},
  year         = {{1994}},
}