@inproceedings{8263,
  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.}},
  author       = {{Andries, Marc and Engels, Gregor}},
  booktitle    = {{Proceedings of the International Workshop on Graph Transformations in Computer Science (1993), Dagstuhl (Germany)}},
  pages        = {{19--36}},
  publisher    = {{Springer}},
  title        = {{{Syntax and Semantics of Hybrid Database Languages}}},
  doi          = {{http://dx.doi.org/10.1007/3-540-57787-4_2}},
  volume       = {{776}},
  year         = {{1994}},
}

@inproceedings{8264,
  author       = {{Engels, Gregor and Groenewegen, Luuk}},
  booktitle    = {{Proceedings of the Third European Workshop on Software Process Technology (EWSPT 1994), Villard de Lans (France)}},
  pages        = {{128--151}},
  publisher    = {{Springer}},
  title        = {{{Specification of coordinated behaviour by SOCCA}}},
  doi          = {{http://dx.doi.org/10.1007/3-540-57739-4_19}},
  year         = {{1994}},
}

@inproceedings{8265,
  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.}},
  author       = {{Engels, Gregor and Löhr, Perdita}},
  booktitle    = {{Proceedings of the 2nd International East/West Database Workshop, Klagenfurt (Germany)}},
  pages        = {{303--314}},
  publisher    = {{Springer}},
  title        = {{{Visual Specification of Complex Database Actions}}},
  year         = {{1994}},
}

@article{7407,
  author       = {{Löhr-Richter, Perdita and Engels, Gregor}},
  journal      = {{GI-Datenbank Rundbrief}},
  pages        = {{33--35}},
  title        = {{{Visuelles Spezifizieren von komplexen Aktionen auf Datenbankstrukturen}}},
  volume       = {{13}},
  year         = {{1994}},
}

@inbook{7512,
  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.}},
  author       = {{Ebert, Jürgen and Engels, Gregor}},
  booktitle    = {{Encyclopedia of Software Engineering}},
  pages        = {{382--394}},
  publisher    = {{John Wiley & Sons, Inc.}},
  title        = {{{Design Representation}}},
  year         = {{1994}},
}

@inbook{7513,
  author       = {{Engels, Gregor and Groenewegen, Luuk}},
  booktitle    = {{Software Process Modelling and Technology}},
  pages        = {{71--102}},
  publisher    = {{Research Studies Press}},
  title        = {{{SOCCA: Specifications of Coordinated and Cooperative Activities}}},
  year         = {{1994}},
}

@inproceedings{7826,
  author       = {{Engels, Gregor and Verrijn-Stuart, A.A.}},
  booktitle    = {{Fortschritt-Berichte VDI}},
  number       = {{251}},
  pages        = {{45--53}},
  publisher    = {{VDI Verlag}},
  title        = {{{Integrationsaspekte bei verteilter Software-Entwicklung}}},
  year         = {{1993}},
}

@techreport{8190,
  author       = {{Andries, Marc and Engels, Gregor}},
  publisher    = {{Vakgroep Informatica, Rijksuniversiteit Leiden}},
  title        = {{{A Hybrid Query Language for the Extended Entity Relationship Model}}},
  year         = {{1993}},
}

@techreport{8191,
  author       = {{Ehrig, Hartmut and Engels, Gregor}},
  publisher    = {{Vakgroep Informatica, Rijksuniversiteit Leiden}},
  title        = {{{Towards a Module Concept for Graph Transformation Systems}}},
  year         = {{1993}},
}

@techreport{8192,
  author       = {{Engels, Gregor and Rozenberg, Grzegorz}},
  publisher    = {{Vakgroep Informatica, Rijksuniversiteit Leiden}},
  title        = {{{Abstracts COMPUGRAPH II Workshop}}},
  year         = {{1993}},
}

@inproceedings{8262,
  author       = {{Engels, Gregor and Groenewegen, Luuk}},
  booktitle    = {{Proceedings of the Workshop on Software Process (ISPW 1993), Wadern (Germany)}},
  pages        = {{66--68}},
  publisher    = {{IEEE Computer Society}},
  title        = {{{Modular, Visual Specifications of Software Processes}}},
  year         = {{1993}},
}

@inproceedings{7825,
  author       = {{Koopman, Pieter and Groenewegen, Luuk and Engels, Gregor}},
  booktitle    = {{Proceedings of the conference SION Computing Science in the Netherlands (CSN '92), The Netherlands}},
  pages        = {{156--167}},
  title        = {{{Functional Description of Parallel Processes}}},
  year         = {{1992}},
}

@techreport{8189,
  author       = {{Engels, Gregor}},
  publisher    = {{Leiden University}},
  title        = {{{Visual Specifications of Conceptual Database Schemata (Abstract)}}},
  year         = {{1992}},
}

@inproceedings{8260,
  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.}},
  author       = {{Engels, Gregor and Löhr-Richter, Perdita}},
  booktitle    = {{Proceedings of the Fifth International Workshop on Computer-Aided Software Engineering (CASE 1992), Montreal (Canada)}},
  pages        = {{19--22}},
  publisher    = {{IEEE Computer Society}},
  title        = {{{CADDY: A Highly Integrated Environment to Support Conceptual Database Design}}},
  year         = {{1992}},
}

@inproceedings{8261,
  author       = {{Engels, Gregor and Groenewegen, Luuk}},
  booktitle    = {{Proceedings of the Second European Workshop on Software Process Technology (EWSPT 92), Trondheim, Norway}},
  pages        = {{58--60}},
  publisher    = {{Springer}},
  title        = {{{Specification of Coordinated Behaviour in the Software Development Process}}},
  doi          = {{http://dx.doi.org/10.1007/BFb0017495}},
  volume       = {{635}},
  year         = {{1992}},
}

@article{7408,
  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.}},
  author       = {{Hohenstein, Uwe and Engels, Gregor}},
  journal      = {{Information Systems}},
  number       = {{3}},
  pages        = {{209--242}},
  title        = {{{SQL/EER - Syntax and Semantics of an Entity-Relationship-Based Query Language}}},
  doi          = {{http://dx.doi.org/10.1016/0306-4379(92)90014-E}},
  volume       = {{17}},
  year         = {{1992}},
}

@article{7409,
  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.}},
  author       = {{Engels, Gregor and Lewerentz, Claus and Nagl, Manfred and Schäfer, Wilhelm and Schürr, Andy}},
  journal      = {{ACM Transactions on Software Engineering and Methodology (TOSEM)}},
  number       = {{2}},
  pages        = {{135--167}},
  title        = {{{Building Integrated Software Development Environments, Part I: Tool Specification}}},
  volume       = {{1}},
  year         = {{1992}},
}

@article{7410,
  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.}},
  author       = {{Engels, Gregor and Gogolla, Martin and Hohenstein, Uwe and Hülsmann, Klaus and Löhr-Richter, Perdita and Saake, Gunter and Ehrich, Hans-Dietrich}},
  journal      = {{Data & Knowledge Engineering}},
  number       = {{2}},
  pages        = {{157--204}},
  title        = {{{Conceptual Modelling of Database Applications Using an Extended ER Model}}},
  doi          = {{http://dx.doi.org/10.1016/0169-023X(92)90008-Y}},
  volume       = {{9}},
  year         = {{1992}},
}

@techreport{8188,
  author       = {{Löhr-Richter, Perdita and Engels, Gregor}},
  publisher    = {{Leiden University}},
  title        = {{{Incremental Design of Conceptual Database Schemata with CADDY}}},
  year         = {{1991}},
}

@inproceedings{7824,
  author       = {{Hohenstein, Uwe and Engels, Gregor}},
  booktitle    = {{Proceedings of the 9th International Conference on Entity-Relationship Approach (ER 90), Lausanne, Switzerland}},
  pages        = {{177--188}},
  publisher    = {{ER Institute}},
  title        = {{{Formal Semantics of an Entity-Relationship Query Language}}},
  year         = {{1990}},
}