Reiko Heckel and Alexey Cherchago: Structural and Behavioural Compatibility of Graphical Service Specifications. In Logic and Algebraic Programming, vol. 70, no. 1, pp. 15--33 (2007)
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@article{Heckel2007, author = {Reiko Heckel and Alexey Cherchago}, title = {Structural and Behavioural Compatibility of Graphical Service Specifications}, journal = {Logic and Algebraic Programming}, year = {2007}, volume = {70}, number = {1}, pages = {15--33}, month = {January} }

The ability of applications to dynamically discover required services is a key motivation for Web Services. However, this aspect is not entirely supported by current Web Services standards. It is our objective to develop a formal approach, allowing the automation of the discovery process. The approach is based on the matching of interface specifications of the required and provided services. In the present paper, we establish an integral notion of structural and behavioural compatibility of service specifications. While structural information is represented by operation declarations, behavioural descriptions are provided by contracts expressed as graph transformation rules with positive and negative application conditions. The integration of structural and behavioural descriptions is facilitated by typed and parameterised graph transformation systems, augmenting the rule-based description of behaviour by a type graph and operation declarations representing the structural aspect. The matching relation taking into account this combination is called parameterised substitution morphism. We show that substitution morphisms satisfy the semantic requirement inherent in its name: the substitutability of abstract operations by (calls to) concrete ones.

Reiko Heckel and Marc Lohmann: Model-Driven Development of Reactive Information Systems: From Graph Transformation Rules to JML Contracts. In International Journal on Software Tools for Technology Transfer (STTT), vol. 9, no. 2, pp. 193--207 (2006)
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@article{Heckel2006, author = {Reiko Heckel and Marc Lohmann}, title = {Model-Driven Development of Reactive Information Systems: From Graph Transformation Rules to JML Contracts}, journal = {International Journal on Software Tools for Technology Transfer (STTT)}, year = {2006}, volume = {9}, number = {2}, pages = {193--207}, month = {August} }

The model-driven architecture focuses on the evolution and integration of applications across heterogeneous platforms by means of generating implementations from platform-independent models. Most of the existing realizations of this idea are limited to static models. We propose a model-driven approach to the development of reactive information systems, like dynamic Web pages or Web services, modeling their typical request-query-update-response pattern by means of graph transformation rules. Rather than generating executable code from these models we focus on the verification of the consistency between different sub-models and an implementation that may have been produced manually. The main technical tool for achieving this goal is a mapping of graph transformation rules to contracts expressed in the Java Modeling Language.

Jan Hendrik Hausmann and Reiko Heckel and Marc Lohmann: Model-based development of Web service descriptions enabling a precise matching concept. In International Journal of Web Services Research, vol. 2, no. 2, pp. 67--85 (2005)
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@article{Hausmann2005, author = {Jan Hendrik Hausmann and Reiko Heckel and Marc Lohmann}, title = {Model-based development of Web service descriptions enabling a precise matching concept}, journal = {International Journal of Web Services Research}, year = {2005}, volume = {2}, number = {2}, pages = {67--85}, month = {April-June} }

Web services are software components that can be discovered and employed at runtime using the Internet. Conflicting requirements towards the nature of these services can be identified. From a business perspective, Web services promise to enable the formation of ad-hoc cooperations on a global scale. From a technical perspective, a high degree of standardization and rigorous specifications are required to enable the automated integration of Web services. A suitable technology for Web services has to mediate these needs for flexibility and stability. To be usable in practice, this technology has to be aligned to standard software engineering practice to allow for a seamless development of Web service enabled components. In this paper, we introduce a new approach to the description of Web services. It is a visual approach based on the use of software models and graph transformations and allows for the flexible description of innovative services while providing a precise matching concept. A methodology enabling the seamless development of such Web service descriptions in the context of a standard model-based development approach is presented.

Luciano Baresi and Reiko Heckel and Sebastian Thöne and Dániel Varró: Style-Based Modeling and Refinement of Service-Oriented Architectures. In Software and Systems Modeling, vol. 5, no. 2, pp. 187-207 (2005)
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@article{Baresi2005, author = {Luciano Baresi and Reiko Heckel and Sebastian Thöne and Dániel Varró}, title = {Style-Based Modeling and Refinement of Service-Oriented Architectures}, journal = {Software and Systems Modeling}, year = {2005}, volume = {5}, number = {2}, pages = {187-207} }

Service-oriented architectures (SOA) provide a flexible and dynamic platform for implementing business solutions. In this paper, we address the modeling of such architectures by refining business-oriented architectures, which abstract from technology aspects, into service-oriented ones, focusing on the ability of dynamic reconfiguration (binding to new services at run-time) typical for SOA. The refinement is based on conceptual models of the platforms involved as architectural styles, formalized by graph transformation systems. Based on a refinement relation between abstract and platform-specific styles we investigate how to realize business-specific scenarios on the SOA platform by automatically deriving refined, SOA-specific reconfiguration scenarios.

Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer: Dynamic Meta Modeling with Time: Specifying the Semantics of Multimedia Sequence Diagrams. In Software and Systems Modeling, vol. 3, no. 3, pp. 181--193 (2004)
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@article{HHS04SoSym, author = {Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer}, title = {Dynamic Meta Modeling with Time: Specifying the Semantics of Multimedia Sequence Diagrams}, journal = {Software and Systems Modeling}, year = {2004}, volume = {3}, number = {3}, pages = {181--193}, month = {August} }

UML offers different diagram types to model behavior and dynamics of software systems. In some domains like embedded real-time systems or multimedia systems, it is necessary to include specifications of time since the correctness of these applications depends on the fulfillment of temporal requirements in addition to functional requirements. UML thus already incorporates language features to model time and temporal constraints. Such model elements must have an equivalent in the semantic domain. We have proposed Dynamic Meta Modeling (DMM) as a means for the specification of the formal operational semantics of UML models by applying graph transformation to the meta modeling of dynamic behavior. Within this paper, we extend this approach to also account for time by building on timed graph transformations. We apply these concepts to the domain of multimedia application modeling in which we adopt UML sequence diagrams. The DMM rules with time then specify an interpreter that can be used to analyze or test a model of multimedia sequence diagrams.

Reiko Heckel and Mercé Llabrés and Hartmut Ehrig and Fernando Orejas: Concurrency and Loose Semantics of Open Graph Transformation Systems. In Mathematical Structures in Computer Science, vol. 12, no. 4, pp. 349--376 (2002)
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@article{HLEO02, author = {Reiko Heckel and Mercé Llabrés and Hartmut Ehrig and Fernando Orejas}, title = {Concurrency and Loose Semantics of Open Graph Transformation Systems}, journal = {Mathematical Structures in Computer Science}, year = {2002}, volume = {12}, number = {4}, pages = {349--376}, month = {August} }

Graph transitions represent an extension of the DPO approach to graph transformation for the specification of reactive systems. In this paper, we develop the theory of concurrency for graph transitions. In particular, we prove a local Church–Rosser theorem and define a notion of shift-equivalence that allows us to represent both intra-concurrency (within the specified subsystem) and inter-concurrency (between subsystem and environment). Via an implementation of transitions in terms of DPO transformations with context rules, a second, more restrictive notion of equivalence is defined that captures, in addition, the extra-concurrency (between operations of the environment). As a running example and motivation, we show how the concepts of this paper provide a formal model for distributed information systems.

Ralph Depke and Reiko Heckel and Jochen Küster: Formal Agent-Oriented Modeling with Graph Transformation. In Science of Computer Programming, vol. 44, pp. 229--252 (2002)
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@article{dhk02scp, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Formal Agent-Oriented Modeling with Graph Transformation}, journal = {Science of Computer Programming}, year = {2002}, volume = {44}, pages = {229--252} }

For the generic specification of protocols, goals, or workflows, many approaches to agentoriented modeling provide a concept of role. Roles abstract from the concrete agents involved in an interaction. They provide means for the evolution of agents and serve as components of agent design. Despite the wide-spread usage of roles in agent-oriented modeling, a systematic analysis of the different aspects and properties of this concept is still missing. In this paper, we perform such an analysis and identify requirements for a general role concept. We develop such a role concept for a modeling approach based on the UML and graph transformation systems and exemplify its use for the specification (and application) of protocols. Finally, we provide a run-time semantics for roles based on concepts from the theory of graph transformation.

Andrea Corradini and Reiko Heckel and Ugo Montanari: Compositional SOS and Beyond: A Coalgebraic View of Open Systems. In Theoretical Computer Science, vol. 280, no. 1-2, pp. 163--192 (2002)
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@article{CHM02a, author = {Andrea Corradini and Reiko Heckel and Ugo Montanari}, title = {Compositional SOS and Beyond: A Coalgebraic View of Open Systems}, journal = {Theoretical Computer Science}, year = {2002}, volume = {280}, number = {1-2}, pages = {163--192}, month = {May} }

In this paper we address the issue of providing a structured coalgebra presentation of transition systems with algebraic structure on states determined by an equational specification . More precisely, we aim at representing such systems as coalgebras for an endofunctor on the category of-algebras. The systems we consider are specified by using arbitrary SOS rules, which in general do not guarantee that bisimilarity is a congruence. We first show that the structured coalgebra representation...

Julia Padberg and Lars Jansen and Hartmut Ehrig and E. Schnieder and Reiko Heckel: Cooperability in Train Control Systems: Specification of Scenarios using Open Nets. In Transactions of the Society for Design and Process Science, vol. 5, no. 1, pp. 3--21 (2001)
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@article{PJE+00, author = {Julia Padberg and Lars Jansen and Hartmut Ehrig and E. Schnieder and Reiko Heckel}, title = {Cooperability in Train Control Systems: Specification of Scenarios using Open Nets}, journal = {Transactions of the Society for Design and Process Science}, year = {2001}, volume = {5}, number = {1}, pages = {3--21} }

We consider the area of train control systems like the European Train Control Systems (ETCS) where several different scenarios are considered and related software components must cooper-ate effectively in order to achieve the desired system behavior. In order to specify operational behavior of ETCS high-level Petri net techniques have been identified as one of the most ade-quate formal specification techniques according to the state of the art. Petri nets can be used to describe scenarios that represent the required operational behavior of the controlled system. Unfortunately, Petri nets in the usual sense are not fully adequate to model such scenarios and to achieve cooperability. This is caused by the lack of Petri nets to interact with the environment. Thus Petri nets fail to provide a suitable notion for cooperability between different components of a system. The new notion of open nets, developed within the research group “Petri Net Tech-nology”, is most promising as a conceptual and formal technique for these kinds of problems. In this paper we study a simplified version of a railway level crossing control system. There are a few number of basic scenarios represented by interaction diagrams, which are modeled by open nets, called scenario nets. The cooperability of system components is ensured by suit-able integration and composition techniques for open nets. These techniques provide a basis for cooperability in train control systems in general, especially for problems in the area of ETCS.

Reiko Heckel and Hartmut Ehrig and Uwe Wolter and Andrea Corradini: Double Pullback Transitions and Coalgebraic Loose Semantics for Graph Transformation Systems. In Applied Categorical Structures, vol. 9, no. 1, pp. 83--110 (2001)
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@article{HEWC01, author = {Reiko Heckel and Hartmut Ehrig and Uwe Wolter and Andrea Corradini}, title = {Double Pullback Transitions and Coalgebraic Loose Semantics for Graph Transformation Systems}, journal = {Applied Categorical Structures}, year = {2001}, volume = {9}, number = {1}, pages = {83--110}, month = {January} }

The aim of this paper is an extension of the theory of graph transformation systems in order to make them suitable for the specification of reactive systems. For this purpose two main extensions of the algebraic theory of graph transformations are proposed. Firstly, graph transitions are introduced as a loose interpretation of graph productions, defined using a double pullback construction in contrast to classical graph derivations based on double-pushouts. Two characterisation results relate ...

Ralph Depke and Reiko Heckel and Jochen Küster: Roles in Agent-Oriented Modeling. In International Journal of Software Engineering and Knowledge Engineering, vol. 11, no. 3, pp. 281--302 (2001)
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@article{DHK01ijseke, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Roles in Agent-Oriented Modeling}, journal = {International Journal of Software Engineering and Knowledge Engineering}, year = {2001}, volume = {11}, number = {3}, pages = {281--302} }

In this paper, we perform such an analysis and identify requirements for a general role concept. We develop such a role concept for a modeling approach based on the UML and graph transformation systems and exemplify its use for the specification (and application) of protocols. Finally, we provide a run-time semantics for roles based on concepts from the theory of graph transformation.

Andrea Corradini and Martin Große-Rhode and Reiko Heckel: A Coalgebraic presentation of structured transition systems. In Theoretical Computer Science, vol. 260, no. 1-2, pp. 27--55 (2001)
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@article{CGH01tcs, author = {Andrea Corradini and Martin Große-Rhode and Reiko Heckel}, title = {A Coalgebraic presentation of structured transition systems}, journal = {Theoretical Computer Science}, year = {2001}, volume = {260}, number = {1-2}, pages = {27--55}, month = {May} }

This paper relates labelled transition systems and coalgebras with the motivation of comparing and combining their complementary contributions to the theory of concurrent systems. The well-known mismatch between these two notions concerning the morphisms is resolved by extending the coalgebraic framework by lax cohomomorphisms.Enriching both labelled transition systems and coalgebras with algebraic structure for an algebraic specification, the correspondence is lost again. This motivates the introduction of lax coalgebras, where the coalgebra structure is given by a lax homomorphism. The resulting category of lax coalgebras and lax cohomomorphisms for a suitable endofunctor is shown to be isomorphic to the category of structured transition systems, where both states and transitions form algebras.The framework is also presented on a more abstract categorical level using monads and comonads, extending the bialgebraic approach introduced by Turi and Plotkin.

Gregor Engels and Reiko Heckel: Graph Transformation and Visual Modeling Techniques. In Bulletin of the EATCS, no. 71, pp. 186--202 (2000)
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@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} }

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.

Ralph Depke and Reiko Heckel and Jochen Küster and Matthew Langham: Agenten im Auftrag des Bankkunden. In Geldinstitute, vol. 31, no. 1-2, pp. 32--33 (2000)
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@article{DHKL00, author = {Ralph Depke and Reiko Heckel and Jochen Küster and Matthew Langham}, title = {Agenten im Auftrag des Bankkunden}, journal = {Geldinstitute}, year = {2000}, volume = {31}, number = {1-2}, pages = {32--33}, month = {Februar } }

Andrea Corradini and Reiko Heckel: Graph Transformation and Visual Modeling Techniques: Workshop Summary and HowTo. In Bulletin of the EATCS, no. 72, pp. 69--76 (2000)
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@article{CH00eatcs, author = {Andrea Corradini and Reiko Heckel}, title = {Graph Transformation and Visual Modeling Techniques: Workshop Summary and HowTo}, journal = {Bulletin of the EATCS}, year = {2000}, number = {72}, pages = {69--76}, month = {October} }

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.

Gregor Engels and Reiko Heckel and Gabriele Taentzer and Hartmut Ehrig: A Combined Reference Model- and View-Based Approach to System Specification. In Int. Journal of Software and Knowledge Engeneering, vol. 7, no. 4, pp. 457--477 (1997)
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@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} }

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.

Annegret Habel and Reiko Heckel and Gabriele Taentzer: Graph Grammars with Negative Application Conditions. In Fundamenta Informaticae, vol. 26, no. 3,4, pp. 287--313 (1996)
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@article{HHT96, author = {Annegret Habel and Reiko Heckel and Gabriele Taentzer}, title = {Graph Grammars with Negative Application Conditions}, journal = {Fundamenta Informaticae}, year = {1996}, volume = {26}, number = {3,4}, pages = {287--313}, month = {June} }

In each graph-grammar approach it is defined how and under which conditions graph productions can be applied to a given graph in order to obtain a derived graph. The conditions under which productions can be applied are called application conditions. Although the generative power of most of the known general graph-grammar approaches is sufficient to generate any recursively enumerable set of graphs, it is often convenient to have specific application conditions for each production. Such application conditions, on the one hand, include context conditions like the existence or non-existence of nodes, edges, or certain subgraphs in the given graph as well as embedding restrictions concerning the morphisms from the left-hand side of the production to the given graph. In this paper, the concept of application conditions introduced by Ehrig and Habel is restricted to contextual conditions, especially negative ones. In addition to the general concept, we state local confluence and the Parallelism Theorem for derivations with application conditions. Finally we study context-free graph grammars with application conditions with respect to their generative power.

Reiko Heckel and Andrea Corradini and Hartmut Ehrig and Michael Löwe: Horizontal and Vertical Structuring of Typed Graph Transformation Systems. In Mathematical Structures in Computer Science, vol. 6, no. 6, pp. 613--648 (1996)
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@article{HCEL96, author = {Reiko Heckel and Andrea Corradini and Hartmut Ehrig and Michael Löwe}, title = {Horizontal and Vertical Structuring of Typed Graph Transformation Systems}, journal = {Mathematical Structures in Computer Science}, year = {1996}, volume = {6}, number = {6}, pages = {613--648} }

Gregor Engels and Marc Lohmann and Stefan Sauer and Reiko Heckel: Model-Driven Monitoring: An Application of Graph Transformation for Design by Contract. In Proceedings of the 3rd International Conference on Graph Transformation (ICGT 2006), Natal (Brazil). Springer (Berlin/Heidelberg), LNCS, vol. 4178, pp. 336--350 (2006)
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@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}, volume = {4178}, series = {LNCS}, pages = {336--350}, address = {Berlin/Heidelberg}, publisher = {Springer} }

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.

Ping Guo and Gregor Engels and Reiko Heckel: Architectural Style - Based Modeling and Simulation of Complex Software Systems. In Proceedings of the 12th Asia-Pacific Software Engineering Conference (APSEC 2005), Taipei (Taiwan). IEEE Computer Society (Washington, DC, USA), pp. 367--374 (2005)
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@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}, address = {Washington, DC, USA}, month = {December}, publisher = {IEEE Computer Society} }

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.

Jan Hendrik Hausmann and Reiko Heckel and Marc Lohmann: Model-based Discovery of Web Services. In Proceedings of the IEEE International Conference on Web Services (ICWS 2004). IEEE Computer Society (Washington, DC, USA), pp. 324--331 (2004)
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@inproceedings{Hausmann2004, author = {Jan Hendrik Hausmann and Reiko Heckel and Marc Lohmann}, title = {Model-based Discovery of Web Services}, booktitle = {Proceedings of the IEEE International Conference on Web Services (ICWS 2004)}, year = {2004}, pages = {324--331}, address = {Washington, DC, USA}, month = {July}, publisher = {IEEE Computer Society} }

Web Services are software components that can be discovered and employed at runtime using the Internet. Conflicting requirements towards the nature of these services can be identified. From a business perspective, Web Services promise to enable the formation of ad-hoc cooperation's on a global scale. From a technical perspective, a high degree of standardization and rigorous specifications are required to enable the automated integration of Web Services. A suitable technology for Web Services has to mediate these needs for flexibility and stability. In this paper, a new approach to the description of Web Service semantics is introduced. It is a visual approach based on the use of software models and graph transformations and allows for the description of innovative services while providing a precise matching concept. An implementation using current standards and tools is available.

Ping Guo and Reiko Heckel: Simulation and Testing of Mobile Computing Systems using Fujaba. In Proceedings of the 2nd International Fujaba Days (2004), Darmstadt (Germany). (Darmstadt, Germany) (2004)
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@inproceedings{Guo2004a, author = {Ping Guo and Reiko Heckel}, title = {Simulation and Testing of Mobile Computing Systems using Fujaba}, booktitle = {Proceedings of the 2nd International Fujaba Days (2004), Darmstadt (Germany)}, year = {2004}, address = {Darmstadt, Germany}, month = {September} }

The paper presents an approach for analysis, modeling and validation of mobile information systems with the tool support of Fujaba. The approach is developed based on UML-like meta models and graph transformation techniques to support sound methodological principals, normal analysis and refinement. With conceptual and concrete level of modeling and simulation, the approach could support application development and the development of new mobile platforms. The approach also provides automatic analysis, validation and behavior consistency check with the support of Fujaba.

Ping Guo and Reiko Heckel: Modeling and Simulation of Context-Aware Mobile Systems. In Proceedings of the 19th IEEE international conference on Automated software engineering (ASE 2004). IEEE Computer Society (Washington, DC, USA), pp. 430--433 (2004)
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@inproceedings{Guo2004, author = {Ping Guo and Reiko Heckel}, title = {Modeling and Simulation of Context-Aware Mobile Systems}, booktitle = {Proceedings of the 19th IEEE international conference on Automated software engineering (ASE 2004)}, year = {2004}, pages = {430--433}, address = {Washington, DC, USA}, publisher = {IEEE Computer Society} }

This paper presents an approach for analysis, design and simulation of mobile systems. The approach is developed based on UML-like meta models and graph transformation techniques to support sound methodological principals, formal analysis and refinement. With conceptual and concrete level of modeling and simulation, the approach could support application development and the development of new mobile platforms.

Alexey Cherchago and Reiko Heckel: Specification Matching of Web Services Using Conditional Graph Transformation Rules. In Proceedings of the conference on Graph Transformation (ICGT 2004), Rome (Italy). Springer (Berlin/Heidelberg), LNCS, vol. 3256 / 2004, pp. 304--318 (2004) Graph Transformations
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@inproceedings{Cherchago2004, author = {Alexey Cherchago and Reiko Heckel}, title = {Specification Matching of Web Services Using Conditional Graph Transformation Rules}, booktitle = {Proceedings of the conference on Graph Transformation (ICGT 2004), Rome (Italy)}, year = {2004}, volume = {3256 / 2004}, series = {LNCS}, pages = {304--318}, address = {Berlin/Heidelberg}, publisher = {Springer}, note = {Graph Transformations} }

The ability of applications to dynamically discover required services is a key problem for Web Services. However, this aspect is not adequately supported by current Web Services standards. It is our objective to develop a formal approach allowing the automation of the discovery process. The approach is based on the matching of requestors requirements for a useful service against service descriptions. In the present paper, we concentrate on behavioral compatibility. This amounts to check a relation between provided and required operations described via operation contracts. Graph transformation rules with positive and negative application conditions are proposed as a visual formal notation for contract specification. We establish the desired semantic relation between requestor and provider and prove the soundness and completeness of a syntactic notion of matching w.r.t. this relation.

Reiko Heckel and Alexey Cherchago: Application of Graph Transformation for Automating Web Service Discovery. In Proceedings of the seminar on Language Engineering for Model-Driven Software Development (2003), Dagstuhl (Germany). Internationales Begegnungs- und Forschungszentrum für Informatik (IBFI) (Dagstuhl, Germany), Dagstuhl Seminar Proceedings (2004)
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@inproceedings{Heckel2004c, author = {Reiko Heckel and Alexey Cherchago}, title = {Application of Graph Transformation for Automating Web Service Discovery}, booktitle = {Proceedings of the seminar on Language Engineering for Model-Driven Software Development (2003), Dagstuhl (Germany)}, year = {2004}, series = {Dagstuhl Seminar Proceedings}, address = {Dagstuhl, Germany}, month = {March}, publisher = {Internationales Begegnungs- und Forschungszentrum für Informatik (IBFI)} }

The paper represents current achievements of an ongoing research that aims to develop a formal approach supporting an automatic selection of a Web service sought by a requestor. The approach is based on the matching the requestor’s requirements for a "useful" service against the service description offered by the provider. We focus on the checking behavioral compatibility between operation contracts specifying pre-conditions and effects of required and provided operations. Graph transformation rules with positive application conditions are proposed as a visual formal notation for contracts. The desired dependence between requestor and provider contracts is determined by the semantic compatibility relation and syntactic matching procedure that is sound w.r.t. this relation.

Reiko Heckel and Ping Guo: Conceptual Modeling of Styles For Mobile Systems: A layered approach based on graph transformation. In Proceedings of the conference on Mobile Information Systems (MOBIS 2004), Oslo (Norway). Springer (Berlin/Heidelberg), IFIP - International Federation for Information Processing, vol. 158, pp. 65--79 (2004)
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@inproceedings{Heckel2004, author = {Reiko Heckel and Ping Guo}, title = {Conceptual Modeling of Styles For Mobile Systems: A layered approach based on graph transformation}, booktitle = {Proceedings of the conference on Mobile Information Systems (MOBIS 2004), Oslo (Norway)}, year = {2004}, volume = {158}, series = {IFIP - International Federation for Information Processing}, pages = {65--79}, address = {Berlin/Heidelberg}, publisher = {Springer} }

When designing a mobile application, we have to be aware of the properties and facilities of the target platform. At a conceptual level, this platform can be specified by a style, defining the structures and operations available to applications. In this paper, we use a UML-like meta model for the structural aspect and graph transformation rules over its instances to specify the dynamics of a style of mobile systems. The model is layered to separate clearly the software from the hardware and the geographic view of the system.

Luciano Baresi and Reiko Heckel and Sebastian Thöne and Dániel Varró: Style-Based Refinement of Dynamic Software Architectures. In Proceedings of the conference on Software Architecture (WICSA 2004), Oslo (Norway). IEEE Computer Society (Washington, DC, USA), pp. 155--166 (2004) 12-15 June 2004
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@inproceedings{Baresi2004, author = {Luciano Baresi and Reiko Heckel and Sebastian Thöne and Dániel Varró}, title = {Style-Based Refinement of Dynamic Software Architectures}, booktitle = {Proceedings of the conference on Software Architecture (WICSA 2004), Oslo (Norway)}, year = {2004}, pages = {155--166}, address = {Washington, DC, USA}, publisher = {IEEE Computer Society}, note = {12-15 June 2004} }

In this paper, we address the correct refinement of abstract architectural models into more platformspecific representations. We consider the challenging case of dynamic architectures which can perform runtime reconfigurations. For this purpose, the underlying platform has to provide the necessary reconfiguration mechanisms. To conceptually model such platforms including provided reconfiguration mechanisms, we use architectural styles formalized by graph transformation rules. Based on formal refinement relations between abstract and platform-specific styles, we can then investigate how to realize business-specific scenarios on a certain platform by automatically deriving refined, platform-specific reconfiguration scenarios.

Reiko Heckel and Marc Lohmann: Model-Based Development of Web Applications Using Graphical Reaction Rules. In Proceedings of the 6th International Conference on Fundamental Approaches to Software Engineering (FASE 2003), Warsaw (Poland). Springer (Berlin/Heidelberg), LNCS, vol. 2621, pp. 170--183 (2003)
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@inproceedings{Heckel2003e, author = {Reiko Heckel and Marc Lohmann}, title = {Model-Based Development of Web Applications Using Graphical Reaction Rules}, booktitle = {Proceedings of the 6th International Conference on Fundamental Approaches to Software Engineering (FASE 2003), Warsaw (Poland)}, year = {2003}, volume = {2621}, series = {LNCS}, pages = {170--183}, address = {Berlin/Heidelberg}, publisher = {Springer} }

The OMG's Model-Driven Architecture focusses on the evolution and integration of applications across heterogeneous middleware platforms. Presently available instances of this idea are mostly limited to static models. We propose a model-driven approach to the development of web-enabled applications, seen as reactive information systems on an HTTP-based communication platform, which covers both static and dynamic aspects. To support the separate change of both platform and functionality we separate at model and implementation level the platform-independent application logic from classes specific to technologies like HTML or SOAP. We discuss a notion of consistency between models at different abstraction levels based on a concept of graphical reaction rules, i.e., graph transformation rules which integrate data state transformation and reactive behavior.

Reiko Heckel and Jochen Küster and Sebastian Thöne and Hendrik Voigt: Towards Consistency of Web Service Architectures. In Proceedings of the 7th World Multiconference on Systemics, Cybernetics, and Informatics (SCI 2003), Orlando, FL (USA). (2003)
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@inproceedings{HKTV03, author = {Reiko Heckel and Jochen Küster and Sebastian Thöne and Hendrik Voigt}, title = {Towards Consistency of Web Service Architectures}, booktitle = {Proceedings of the 7th World Multiconference on Systemics, Cybernetics, and Informatics (SCI 2003), Orlando, FL (USA)}, year = {2003}, month = {July} }

Web services are self-descriptive software components which can automatically be discovered and engaged, together with other web components, to complete tasks over the Internet. The integration of Web services entails consistency problems which can best be solved at the level of models. In this paper, we discuss an approach to model-based consistency management for component-based architectures and its application to Web service architectures.

Gregor Engels and Jochen Küster and Reiko Heckel and Marc Lohmann: Model Based Verification and Validation of Properties. In Proceedings of the conference on Uniform Approaches to Graphical Process Specification Techniques (UNIGRA 2003, Satellite Event of the ETAPS 2003), Warsaw (Poland). Elsevier, Electronic Notes in Theoretical Computer Science, vol. 82, no. 7, pp. 1--18 (2003)
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@inproceedings{Engels2003c, author = {Gregor Engels and Jochen Küster 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}, volume = {82}, number = {7}, series = {Electronic Notes in Theoretical Computer Science}, pages = {1--18}, month = {June}, publisher = {Elsevier} }

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.

Gregor Engels and Reiko Heckel and Jochen Küster: The Consistency Workbench: A Tool for Consistency Management in UML-based Development. In Proceedings of the 6th International Conference on The Unified Modeling Language: Modeling Languages and Applications (UML 2003), San Francisco, CA (USA). Springer (Berlin/Heidelberg), LNCS, vol. 2863, pp. 356--359 (2003)
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@inproceedings{Engels2003b, author = {Gregor Engels and Reiko Heckel and Jochen Küster}, 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}, volume = {2863}, series = {LNCS}, pages = {356--359}, address = {Berlin/Heidelberg}, publisher = {Springer} }

With the Unified Modeling Language becoming applied in diverse contexts, the ability of defining and checking customized consistency conditions is gaining increasing importance. In this paper, we introduce the Consistency Workbench for defining and establishing consistency in a UML-based development process.

Jochen Küster and Reiko Heckel and Gregor Engels: Defining and Validating Transformations of UML Models. In Proceedings of the conference on Human Centric Computing Languages and Environments (HCC 2003), Auckland (New Zealand). IEEE Computer Society (Washington, DC, USA), pp. 145--152 (2003)
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@inproceedings{KusterHE03, author = {Jochen Küster 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}, address = {Washington, DC, USA}, publisher = {IEEE Computer Society} }

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.

Hendrik Voigt and Reiko Heckel: Model-Based Development of Executable Business Processes for Web Services. In Proceedings of Lectures on Concurrency and Petri Nets, Advances in Petri Nets (ACPN 2003), Eichstätt, Germany. Springer (Berlin/Heidelberg), vol. 3098, pp. 559--584 (2003)
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@inproceedings{HeVo2003, author = {Hendrik Voigt and Reiko Heckel}, title = {Model-Based Development of Executable Business Processes for Web Services}, booktitle = {Proceedings of Lectures on Concurrency and Petri Nets, Advances in Petri Nets (ACPN 2003), Eichstätt, Germany}, year = {2003}, volume = {3098}, pages = {559--584}, address = {Berlin/Heidelberg}, month = {September}, publisher = {Springer} }

In order to implement business processes, the composition of simpler services provided by different independent participants requires a high degree of standardization and flexibility. For this purpose, platform-independent XML-based languages like the Business Process Execution Language for Web Services (BPEL4WS) are suitable. XML documents are in fact human readable, but in general they are hard to produce and to understand by business experts which are, however, most qualified for defining business processes. We present a model-based development method based on an intuitive and adequate modelling notation, an automatic transformation of process models to their XML-based encoding, and techniques to analyze processes. In this context the Unified Modeling Language (UML) as standard notation for modelling software, graph transformation as meta language for defining model transformations, and a semantic interpretation of process models in terms of Communicating Sequential Processes (CSP) are used.

Luciano Baresi and Reiko Heckel and Sebastian Thöne and Dániel Varró: Modeling and validation of service-oriented architectures: application vs. style. In Proceedings of the European Software Engineering Conference and ACM SIGSOFT Symposium on the Foundations of Software Engineering (ESEC/FSE 2003), Helsinki (Finland). ACM Press (New York, NY, USA), pp. 68--77 (2003)
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@inproceedings{Baresi2003, author = {Luciano Baresi and Reiko Heckel and Sebastian Thöne and Dániel Varró}, title = {Modeling and validation of service-oriented architectures: application vs. style}, booktitle = {Proceedings of the European Software Engineering Conference and ACM SIGSOFT Symposium on the Foundations of Software Engineering (ESEC/FSE 2003), Helsinki (Finland)}, year = {2003}, pages = {68--77}, address = {New York, NY, USA}, month = {September}, publisher = {ACM Press} }

Most applications developed today rely on a given middleware platform which governs the interaction between components, the access to resources, etc. To decide, which platform is suitable for a given application (or more generally, to understand the interaction between application and platform), we propose UML models of both the architectural style of the platform and the application scenario. Based on a formal interpretation of these as graphs and graph transformation systems, we are able to validate the consistency between platform and application. We exemplify the approach for platforms realizing the service-oriented architectural style and a supply chain management system as application scenario. Besides, we demonstrate the potential of model checking for graph transformation systems for answering the above consistency question.

Reiko Heckel and Jochen Küster and Gabriele Taentzer: Confluence of Typed Attributed Graph Transformation Systems. In Proceedings of the First International Conference on Graph Transformation (ICGT 2002), Barcelona (Spain). Springer (Berlin/Heidelberg), pp. 161--176 (2002)
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@inproceedings{Heckel2002, author = {Reiko Heckel and Jochen Küster and Gabriele Taentzer}, title = {Confluence of Typed Attributed Graph Transformation Systems}, booktitle = {Proceedings of the First International Conference on Graph Transformation (ICGT 2002), Barcelona (Spain)}, year = {2002}, pages = {161--176}, address = {Berlin/Heidelberg}, month = {October }, publisher = {Springer} }

The issue of confluence is of major importance for the successful application of attributed graph transformation, such as automated translation of UML models into semantic domains. Whereas termination is undecidable in general and must be established by carefully designing the rules, local confluence can be shown for term rewriting and graph rewriting using the concept of critical pairs. In this paper, we discuss typed attributed graph transformation using a new simplified notion of attribution. For this kind of attributed graph transformation systems we establish a definition of critical pairs and prove a critical pair lemma, stating that local confluence follows from confluence of all critical pairs.

Reiko Heckel and Mourad Chouikha: Compositional Control Synthesis for Discrete Event Systems: An Approach based on Open Petri Nets. In Proceedings of the conference on Integrated Design & Process Technology (IDPT 2002), Pasadena, CA (USA). Society of Design and Process Science (Grandview, TX, USA), pp. 63-77 (2002) Sixth World Conference on Integrated Design & Process Technology (IDPT 2002)
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@inproceedings{Heckel02, author = {Reiko Heckel and Mourad Chouikha}, title = {Compositional Control Synthesis for Discrete Event Systems: An Approach based on Open Petri Nets}, booktitle = {Proceedings of the conference on Integrated Design & Process Technology (IDPT 2002), Pasadena, CA (USA)}, year = {2002}, pages = {63-77}, address = {Grandview, TX, USA}, month = {June}, publisher = {Society of Design and Process Science}, note = {Sixth World Conference on Integrated Design & Process Technology (IDPT 2002)} }

Open nets are place-transition Petri nets with interfaces, which support a notion of composition and a corresponding compositional interpretation of the concurrent behaviour of nets. The control synthesis problem of generating a controller for a given plant from an abstract specification of the controller’s behaviour can be formulated in terms of open nets bymodelling the plant as an open net whose interfaces correspond to the sensors and actuators of the controller and specifying the desired behaviour as a set of processes for this net. Then, the problem consists in synthesising a controller net which, when composed with the net modelling the plant, leads to the specified restriction of the plant’s processes. Based on this observation, which provides an abstraction of the actual synthesis algorithm, we study the problem of generating controllers consisting of several components. In particular, we analyse requirements for the logic used for specifying the controller in order to allow for a compositional, component-wise synthesis.

Jan Hendrik Hausmann and Reiko Heckel and Gabriele Taentzer: Detecting conflicting functional requirements in a use case driven approach: A static analysis technique based on graph transformation. In Proceedings of the 24th International Conference on Software Engineering (ICSE 2002), Orlando, FL (USA). ACM Press (New York, NY, USA), pp. 105--155 (2002)
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@inproceedings{Hausmann2002, author = {Jan Hendrik Hausmann and Reiko Heckel and Gabriele Taentzer}, title = {Detecting conflicting functional requirements in a use case driven approach: A static analysis technique based on graph transformation}, booktitle = {Proceedings of the 24th International Conference on Software Engineering (ICSE 2002), Orlando, FL (USA)}, year = {2002}, pages = {105--155 }, address = {New York, NY, USA}, month = {Mai}, publisher = {ACM Press} }

In object-oriented software development, requirements of different stakeholders are often manifested in use case models which complement the static domain model by dynamic and functional requirements. In the course of development, these requirements are analyzed and integrated to produce a consistent overall requirements specification. Iterations of the model may be triggered by conflicts between requirements of different parties.However, due to the diversity, incompleteness, and informal nature, in particular of functional and dynamic requirements, such conflicts are difficult to find. Formal approaches to requirements engineering, often based on logic, attack these problems, but require highly specialized experts to write and reason about such specifications.In this paper, we propose a formal interpretation of use case models consisting of UML use case, activity, and collaboration diagrams. The formalization, which is based on concepts from the theory of graph transformation, allows to make precise the notions of conflict and dependency between functional requirements expressed by different use cases. Then, use case models can be statically analyzed, and conflicts or dependencies detected by the analysis can be communicated to the modeler by annotating the model.An implementation of the static analysis within a graph transformation tool is presented.

Szilvia Gyapay and Reiko Heckel and Dániel Varró: Graph Transformation with Time: Causality and Logical Clocks. In Proceedings of the First International Conference on Graph Transformation (ICGT 2002), Barcelona (Spain). Springer (Berlin/Heidelberg), LNCS, vol. 2505, pp. 120--134 (2002)
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@inproceedings{Gyapay2002, author = {Szilvia Gyapay and Reiko Heckel and Dániel Varró}, title = {Graph Transformation with Time: Causality and Logical Clocks}, booktitle = {Proceedings of the First International Conference on Graph Transformation (ICGT 2002), Barcelona (Spain)}, year = {2002}, volume = {2505}, series = {LNCS}, pages = {120--134}, address = {Berlin/Heidelberg}, month = {October}, publisher = {Springer} }

Following TER nets, an approach to the modelling of time in high-level Petri nets, we propose a model of time within (attributed) graph transformation systems where logical clocks are represented as distinguished node attributes. Corresponding axioms for the time model in TER nets are generalised to graph transformation systems and semantic variations are discussed. They are summarised by a general theorem ensuring the consistency of temporal order and casual dependencies. The resulting notions of typed graph transformation with time specialise the algebraic doublepushout (DPO) approach to typed graph transformation. In particular, the concurrency theory of the DPO approach can be used in the transfer of the basic theory of TER nets. 1.

Gregor Engels and Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer: Testing the Consistency of Dynamic UML Diagrams. In Proceedings of the Sixth International Conference on Integrated Design and Process Technology (IDPT 2002), Pasadena, CA (USA). (2002) Pasadena, CA, USA
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@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} }

Gregor Engels and Reiko Heckel and Jochen Küster and Luuk Groenewegen: Consistency-Preserving Model Evolution through Transformations. In Proceedings of the 5th International Conference on The Unified Modeling Language (UML 2002), Dresden (Germany). Springer (Berlin/Heidelberg), LNCS, vol. 2460, pp. 212--226 (2002)
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@inproceedings{Engels02a, author = {Gregor Engels and Reiko Heckel and Jochen Küster 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}, volume = {2460}, series = {LNCS}, pages = {212--226}, address = {Berlin/Heidelberg}, month = {Oktober}, publisher = {Springer} }

Luciano Baresi and Reiko Heckel: Tutorial Introduction to Graph Transformation: A Software Engineering Perspective. In Proceedings of the 1st International Conference on Graph Transformation (ICGT 2002), Barcelona (Spain). Springer (Berlin/Heidelberg), LNCS, vol. 2505, pp. 402--429 (2002)
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@inproceedings{Baresi2002, author = {Luciano Baresi and Reiko Heckel}, title = {Tutorial Introduction to Graph Transformation: A Software Engineering Perspective}, booktitle = {Proceedings of the 1st International Conference on Graph Transformation (ICGT 2002), Barcelona (Spain)}, year = {2002}, volume = {2505}, series = {LNCS}, pages = {402--429}, address = {Berlin/Heidelberg}, month = {October }, publisher = {Springer} }

Reiko Heckel and Albert Zündorf: How to Specify a Graph Transformation Approach - A Meta Model for Fujaba. In H. Ehrig and J. Padberg (eds.): {Proceeding of the workshop on Uniform Approaches to Graphical Process Specifcation Techniques (UNIGRA 2001, satellite event of the ETAPS 2001), Genova (Italy). Elsevier, Electronic Notes in Theoretical Computer Science, vol. 44, pp. 41-51 (2001)
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@inproceedings{Heckel2001, author = {Reiko Heckel and Albert Zündorf}, editor = {H. Ehrig and J. Padberg}, title = {How to Specify a Graph Transformation Approach - A Meta Model for Fujaba}, booktitle = {{Proceeding of the workshop on Uniform Approaches to Graphical Process Specifcation Techniques (UNIGRA 2001, satellite event of the ETAPS 2001), Genova (Italy)}, year = {2001}, volume = {44}, series = {Electronic Notes in Theoretical Computer Science}, pages = {41-51}, publisher = {Elsevier} }

Reiko Heckel and Stefan Sauer: Strengthening UML Collaboration Diagrams by State Transformations. In Proceedings of the 4th International Conference on Fundamental Approaches to Software Engineering (FASE 2001), Genova (Italy). Springer (London, UK), LNCS, vol. 2029, pp. 109--123 (2001)
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@inproceedings{Heckel2001b, author = {Reiko Heckel and Stefan Sauer}, title = {Strengthening UML Collaboration Diagrams by State Transformations}, booktitle = {Proceedings of the 4th International Conference on Fundamental Approaches to Software Engineering (FASE 2001), Genova (Italy)}, year = {2001}, volume = {2029}, series = {LNCS}, pages = {109--123}, address = {London, UK}, month = {April}, publisher = {Springer} }

Collaboration diagrams as described in the official UML documents specify patterns of system structure and interaction. In this paper, we propose their use for specifying, in addition, pre/postconditions and state transformations of operations and scenarios. This conceptual idea is formalized by means of graph transformation systems and graph process, thereby integrating the state transformation with the structural and the interaction aspect.

Reiko Heckel: Open Petri Nets as Semantic Model for Business Process Integration. In Proceedings of the 2nd International Colloquium on Petri Net Technologies for Modelling Communication Based Systems. DFG Research Group "Petri Net Technology", pp. 129--134 (2001)
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@inproceedings{Hec01, author = {Reiko Heckel}, title = {Open Petri Nets as Semantic Model for Business Process Integration}, booktitle = {Proceedings of the 2nd International Colloquium on Petri Net Technologies for Modelling Communication Based Systems}, year = {2001}, pages = {129--134}, month = {September}, publisher = {DFG Research Group "Petri Net Technology"} }

One important application of Petri nets is thespecification of workflows. Such a specification is needed, for example, when interoperability of the workflows is an issue, which is frequently the case when business processes of different organizations shall be integrated.A workflow net is a Petri net satisfying some structural constraints, like the existence of one initial and one final place, and a corresponding soundness condition.An interorganizational workflow is modeled as a set of such workflow nets connected through additional places for asynchronous communication and synchronization requirements on transitions.In this contribution we interpret an interorganizational workflow as acomposition of open nets. This allows us to project processes of the overall net to open processes of the local nets and,vice versa, to deduce the global behavior from the behavior of the components.Such a compositional uunderstanding of workflows can be used to simulate and test local workflow nets in an unknown environment, and it provides the semantic justification for reusable components.

Jan Hendrik Hausmann and Reiko Heckel: Use Cases as views: A formal approach to Requirements engineering in the Unified Process. In Proceedings of the GI/OCG-Jahrestagung on Wirtschaft und Wissenschaft in der Network Economy - Visionen und Wirklichkeit (2001), Wien (Österreich). Österreichische Computer Gesellschaft (Wien (Österreich)), vol. 1, pp. 595--599 (2001)
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@inproceedings{Hausmann2001a, author = {Jan Hendrik Hausmann and Reiko Heckel}, title = {Use Cases as views: A formal approach to Requirements engineering in the Unified Process}, booktitle = {Proceedings of the GI/OCG-Jahrestagung on Wirtschaft und Wissenschaft in der Network Economy - Visionen und Wirklichkeit (2001), Wien (Österreich)}, year = {2001}, volume = {1}, pages = {595--599}, address = {Wien (Österreich)}, month = {September}, publisher = {Österreichische Computer Gesellschaft} }

In Requirements Engineering structural and functional requirements for a new software system are gathered, analyzed, and manifested. Unfortunately the connection between these aspects gets lost in the standard object oriented methodology and has to be re-established later on. Not only is this tedious work but the detection of conflicts and inconsistencies in early phases is hindered by the separation of static and dynamic aspects. We propose the use of graph transformations to specify the connection between these aspects. Based on what we call an integrated business model, consistency analysis at the requirements model level becomes possible. Keywords: UML, Unified Process, functional specifications, integrated business model, graph transformation 1 Introduction At the beginning of each software development there are several ideas or visions of what the system to be build should achieve. The techniques developed in the area of requirements engineering are concerned with gathering, structuring and integrating these different ideas for the new system. It is the goal of this process to achieve a set of reasonable and consistent requirements for the further development process. The main problem is the detection and resolution of inconsistencies and conflicts between competing requirements. The application of formal methods and notations promises to support this task by enabling automated analysis. Although multiple formal methods have been proposed by scientists (see e.g. [7] for a survey), the standard methodologies in object oriented software engineering still use very informal and imprecise techniques in this phase of the development process. In particular, what is missing is a coupling between the structural (data) description (captured in class diagrams) and the behavior of the system (captured in activity and use case diagrams). In this paper we will show how to improve this situation by giving use cases a precise description, thus achieving a coupling of the dynamic and static parts of the model. This allows to apply formal techniques of consistency analysis. The paper is organized as follows: Section 2 gives an introduction to the requirements analysis phase in the Unified Process (UP) and points out some weak points of this approach. We will advance the basic ideas presented in the UP by further elaborating the ideas of a business model and formalizing their notion in Section 3. Section 4 introduces use case diagrams and their new role in the context of the integrated business model. Section 5 extends the notion of views to structure the whole requirements model and the concluding Section 6 gives perspectives toward further work on this topic.

Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer: Towards Dynamic Meta Modeling of UML Extensions: An Extensible Semantics for UML Sequence Diagrams. In Proceedings of the IEEE Symposia on Human Centric Computing Languages and Environments (HCC 2001), Stresa (Italy). IEEE Computer Society (Washington, DC, USA), pp. 80--87 (2001)
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@inproceedings{Hausmann2001, author = {Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer}, title = {Towards Dynamic Meta Modeling of UML Extensions: An Extensible Semantics for UML Sequence Diagrams}, booktitle = {Proceedings of the IEEE Symposia on Human Centric Computing Languages and Environments (HCC 2001), Stresa (Italy)}, year = {2001}, pages = {80--87}, address = {Washington, DC, USA}, month = {September}, publisher = {IEEE Computer Society} }

The Unified Modeling Language (UML) still lacks a formal and commonly agreed specification of its semantics that also accounts for UML’s built-in semantic variation points and extension mechanisms. The semantics specification of such extensions must be formally integrated and consistent with the standard UML semantics without changing the latter. Feasible semantics approaches must thus allow advanced UML modelers to define domain-specific language extensions in a precise, yet usable manner. We have proposed dynamic meta modeling for specifying operational semantics of UML behavioral diagrams based on UML collaboration diagrams that are interpreted as graph transformation rules. Herein we show how this approach can be advanced to specify the semantics of UML extensions. As a case study we specify the operational semantics of UML sequence diagrams and extend this specification to include features for modeling multimedia applications.

Reiko Heckel and Gregor Engels: Graph Transformation as a Meta Language for Dynamic Modeling and Model Evolution. In 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). Universidade Nova de Lisboa (Lisbon), no. UNL-DI-1-2001, pp. 42-47 (2001)
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@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}, number = {UNL-DI-1-2001}, pages = {42-47}, address = {Lisbon}, publisher = {Universidade Nova de Lisboa} }

Gregor Engels and Jochen Küster and Luuk Groenewegen and Reiko Heckel: A methodology for specifying and analyzing consistency of object-oriented behavioral models. In 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). ACM Press (New York, NY, USA), vol. 26, no. 5, pp. 186--195 (2001)
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@inproceedings{EngelsKGH2001b, author = {Gregor Engels and Jochen Küster 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}, volume = {26}, number = {5}, pages = {186--195}, address = {New York, NY, USA}, month = {September }, publisher = {ACM Press} }

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.

Gregor Engels and Reiko Heckel and Jochen Küster: Rule-Based Specification of Behavioral Consistency Based on the UML Meta-model. In Proceedings of the conference on The Unified Modeling Language, Modeling Languages, Concepts, and Tools (UML 2001), Toronto (Canada). Springer (Berlin/Heidelberg), vol. 2185, pp. 272--287 (2001)
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@inproceedings{Engels2001a, author = {Gregor Engels and Reiko Heckel and Jochen Küster}, 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}, volume = {2185}, pages = {272--287}, address = {Berlin/Heidelberg}, month = {October}, publisher = {Springer} }

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 the issue 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.

Ralph Depke and Reiko Heckel: Modellierung von Prozessen mit UML und Realisierung durch eine Internet-Agentenplattform. In Proceedings of the 9. Kolloquium Software-Entwicklung für Internet und Intranet, Ostfildern (Germany). Technische Akademie Esslingen (2001)
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@inproceedings{Depke01, author = {Ralph Depke and Reiko Heckel}, title = {Modellierung von Prozessen mit UML und Realisierung durch eine Internet-Agentenplattform}, booktitle = {Proceedings of the 9. Kolloquium Software-Entwicklung für Internet und Intranet, Ostfildern (Germany)}, year = {2001}, month = {September}, publisher = {Technische Akademie Esslingen} }

Workflow management systems provide a facility to execute processes, i.e., workflows by interpretation of process descriptions. The use of process descriptions allows the flexible specification of behavior in a problem oriented way. A system can evolve by just changing the process descriptions. These characteristics are useful not only for workflow management systems but also for general information systems. It has been shown that the activity diagrams of the Unified Modeling Language (UML) can be used for process or workflow descriptions. In a recent project, activity diagrams have been used for specifying complete workflow models that are executed within an agent based workflow management system. Software agents provide advantages that make them useful for the realization of workflow management systems. Such an agent based workflow execution platform has been developed by use of present technology for web information systems. Especially, the eXtensible Markup Language (XML) has been used extensively because it is flexible and it is inherently able to homogenize different kinds of data processing activities within a system.

Ralph Depke and Reiko Heckel and Jochen Küster: Improving the Agent-Oriented Modeling Process with Roles. In Proceedings of the Fifth International Conference on Autonomous Agents (AGENTS 2001), Montreal (Canada). ACM Press (New York, NY, USA), pp. 640-647 (2001)
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@inproceedings{Depke2001, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Improving the Agent-Oriented Modeling Process with Roles}, booktitle = {Proceedings of the Fifth International Conference on Autonomous Agents (AGENTS 2001), Montreal (Canada)}, year = {2001}, pages = {640-647}, address = {New York, NY, USA}, month = {Juni}, publisher = {ACM Press} }

The agent-oriented modeling process is divided in a typical sequence of activities, i.e., requirements specification, analysis, and design. The requirements are specified by descriptions of the system’s functionality and by exemplary scenarios of essential interactions. In analysis the system’s structure is captured and mandatory behavior of agents is prescribed. The design model describes system behavior by means of local operations. The problem arises how the transition between these different stages of the modeling process can be performed. In this paper, we introduce a concept of roles in order to support the transition in a systematic way and thereby improving the agent-oriented modeling process.

Paolo Baldan and Andrea Corradini and Hartmut Ehrig and Reiko Heckel: Compositional Modeling of Reactive Systems Using Open Nets. In Proceedings of the conference on Concurrency Theory (CONCUR 2001), Aalborg (Denmark). Springer (Berlin/Heidelberg), LNCS, vol. 2154, pp. 502--518 (2001)
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@inproceedings{Baldan2001, author = {Paolo Baldan and Andrea Corradini and Hartmut Ehrig and Reiko Heckel}, title = {Compositional Modeling of Reactive Systems Using Open Nets}, booktitle = {Proceedings of the conference on Concurrency Theory (CONCUR 2001), Aalborg (Denmark)}, year = {2001}, volume = {2154}, series = {LNCS}, pages = {502--518}, address = {Berlin/Heidelberg}, month = {August }, publisher = {Springer} }

In order to model the behaviour of open concurrent systems by means of Petri nets, we introduce open Petri nets, a generalization of the ordinary model where some places, designated as open, represent an interface of the system towards the environment. Besides generalizing the token game to reflect this extension, we define a truly concurrent semantics for open nets by extending the Goltz-Reisig process semantics of Petri nets.We introduce a composition operation over open nets, characterized as a pushout in the corresponding category, suitable to model both interaction through open places and synchronization of transitions. The process semantics is shown to be compositional with respect to such composition operation. Technically, our result is similar to the amalgamation theorem for data-types in the framework of algebraic specifications. A possible application field of the proposed constructions and results is the modeling of interorganizational workflows, recently studied in the literature. This is illustrated by a running example.

Gregor Engels and Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer: Dynamic Meta-Modeling: A Graphical Approach to the Operational Semantics of Behavioral Diagrams in UML. In Proceedings of the 3rd international conference on the Unified Modeling Language (UML 2000), York (UK). Springer (Berlin/Heidelberg), LNCS, vol. 1939, pp. 323--337 (2000) Third International Conference
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@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}, volume = {1939}, series = {LNCS}, pages = {323--337}, address = {Berlin/Heidelberg}, publisher = {Springer}, note = {Third International Conference} }

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.

Gregor Engels and Reiko Heckel and Stefan Sauer: UML - A Universal Modeling Language?. In Proceedings of the 21st International Conference on Application and Theory of Petri Nets (ICATPN 2000), Aarhus (Denmark). Springer (Berlin/Heidelberg), LNCS, vol. 1825, pp. 24--38 (2000)
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@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}, volume = {1825}, series = {LNCS}, pages = {24--38}, address = {Berlin/Heidelberg}, month = {June}, publisher = {Springer} }

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.

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

Ralph Depke and Reiko Heckel and Jochen Küster: Integrating visual modeling of agent-based and object-oriented systems. In Proceedings of the conference on Autonomous agents (AGENTS 2000), Barcelona (Spain). ACM Press (New York, NY, USA), pp. 82--83 (2000)
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@inproceedings{Depke2000a, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Integrating visual modeling of agent-based and object-oriented systems}, booktitle = {Proceedings of the conference on Autonomous agents (AGENTS 2000), Barcelona (Spain)}, year = {2000}, pages = {82--83}, address = {New York, NY, USA}, month = {June}, publisher = {ACM Press} }

A concept of roles is introduced for a more fine-grained modeling of objects’ and agents’ structure and behavior. As requirement specification, global graph transformation rules determine the overall effect of the interaction among agents and objects while abstracting form the communication involved. On the design level they describe local autonomous operations by which agents may react to changes in their environment.

Reiko Heckel: Modeling Agent-Based Systems with Graph Transformation and UML. In Proceedings of the Dagstuhl-Seminar 99451 on Rigorous Analysis and Design for Software Intensive Systems. , no. 258 (1999)
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@inproceedings{Hec99, author = {Reiko Heckel}, title = {Modeling Agent-Based Systems with Graph Transformation and UML}, booktitle = {Proceedings of the Dagstuhl-Seminar 99451 on Rigorous Analysis and Design for Software Intensive Systems}, year = {1999}, number = {258} }

Fabio Gadducci and Reiko Heckel and Mercé Llabrés: A Bi-Categorical Axiomatisation of Concurrent Graph Rewriting. In Proceedings of the 8th Conference on Category Theory and Computer Science (CTCS 1999), Edinburgh (UK). Elsevier, Electronic Notes in Theoretical Computer Science, vol. 29, pp. 80--100 (1999)
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@inproceedings{Gadducci1999, author = {Fabio Gadducci and Reiko Heckel and Mercé Llabrés}, title = {A Bi-Categorical Axiomatisation of Concurrent Graph Rewriting}, booktitle = {Proceedings of the 8th Conference on Category Theory and Computer Science (CTCS 1999), Edinburgh (UK)}, year = {1999}, volume = {29}, series = {Electronic Notes in Theoretical Computer Science}, pages = {80--100}, month = {September }, publisher = {Elsevier} }

In this paper the concurrent semantics of double-pushout (DPO) graph rewriting, which is classically defined in terms of shift-equivalence classes of graph derivations, is axiomatised via the construction of a free monoidal bi-category. In contrast to a previous attempt based on 2-categories, the use of bi-categories allows to define rewriting on concrete graphs. Thus, the problem of composition of isomorphism classes of rewriting sequences is avoided. Moreover, as a first step towards the recovery of the full expressive power of the formalism via a purely algebraic description, the concept of disconnected rules is introduced, i.e., rules whose interface graphs are made of disconnected nodes and edges only. It is proved that, under reasonable assumptions, rewriting via disconnected rules enjoys similar concurrency properties like in the classical approach.

Andrea Corradini and Reiko Heckel and Ugo Montanari: Tile Transition Systems as Structured Coalgebras. In Proceedings of the 12th International Symposium on Fundamentals of Computation Theory (FCT '99). Springer (Berlin/Heidelberg), LNCS, vol. 1684, pp. 13--38 (1999)
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@inproceedings{Corradini1999b, author = {Andrea Corradini and Reiko Heckel and Ugo Montanari}, title = {Tile Transition Systems as Structured Coalgebras}, booktitle = {Proceedings of the 12th International Symposium on Fundamentals of Computation Theory (FCT '99)}, year = {1999}, volume = {1684}, series = {LNCS}, pages = {13--38}, address = {Berlin/Heidelberg}, publisher = {Springer} }

The aim of this paper is to investigate the relation between two models of concurrent systems: tile rewrite systems and coalgebras. Tiles are rewrite rules with side effects which are endowed with operations of parallel and sequential composition and synchronization. Their models can be described as monoidal double categories. Coalgebras can be considered, in a suitable mathematical setting, as dual to algebras. They can be used as models of dynamical systems with hidden states in order to study concepts of observational equivalence and bisimilarity in a more general setting. In order to capture in the coalgebraic presentation the algebraic structure given by the composition operations on tiles, coalgebras have to be endowed with an algebraic structure as well. This leads to the concept of structured coalgebras, i.e., coalgebras for an endofunctor on a category of algebras. However, structured coalgebras are more restrictive than tile models. Those models which can be presented as structured coalgebras are characterized by the so-called horizontal decomposition property, which, intuitively, requires that the behavior is compositional in the sense that all transitions from complex states can be derived by composing transitions out of component states.

Julia Padberg and Lars Jansen and Reiko Heckel and Hartmut Ehrig: Interoperability in Train Control Systems: Specification of Scenarios Using Open Nets. In Proceedings of the conference on Integrated Design and Process Technology (IDPT 1998), Berlin (Germany). Society for Design and Process Science, pp. 17--28 (1998)
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@inproceedings{Padberg1998, author = {Julia Padberg and Lars Jansen and Reiko Heckel and Hartmut Ehrig}, title = {Interoperability in Train Control Systems: Specification of Scenarios Using Open Nets}, booktitle = {Proceedings of the conference on Integrated Design and Process Technology (IDPT 1998), Berlin (Germany)}, year = {1998}, pages = {17--28}, month = {October}, publisher = {Society for Design and Process Science} }

We consider the area of train control systems like the European Train Control Systems ETCS where several different scenarios are considered and accordant software components must interoperate effectively in order to achieve the desired system behaviour. In order to specify corresponding problems for ETCS high-level Petri net techniques have been identified as one of the most adequate formal specification technique according to the state of the art. Unfortunately, Petri nets in the usual sense are not fully adequate to model such scenarios and to achieve interoperability. The new notion of open nets, developed within the DFG-Research Group Petri Net Technology, is most promising as a conceptual and formal technique for these kinds of problems. In this paper we study a simplified version of a railway crossing control system with a few number of basic scenarios represented by interaction diagrams, which are modelled by open nets, called scenario nets. The interoperability of system components is specified by suitable integration and composition techniques for open nets. These techniques should be a basis for interoperability in train control systems in general, especially for real problems in the area of ETCS.

Reiko Heckel: Compositional Verification of Reactive Systems Specified by Graph Transformation. In Proceedgins of the First International Conference on Fundamental Approaches to Software Engineering (FASE 1998), Lisbon (Portugal). Springer (Berlin/Heidelberg), LNCS, vol. 1382, pp. 138--153 (1998)
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@inproceedings{Heckel1998a, author = {Reiko Heckel}, title = {Compositional Verification of Reactive Systems Specified by Graph Transformation}, booktitle = {Proceedgins of the First International Conference on Fundamental Approaches to Software Engineering (FASE 1998), Lisbon (Portugal)}, year = {1998}, volume = {1382}, series = {LNCS}, pages = {138--153}, address = {Berlin/Heidelberg}, publisher = {Springer} }

A loose semantics for graph transformation rules which has been developed recently is used in this paper for the compositional verification of specifications. The main conceptual tool here is the notion of view , that is, an incomplete specification describing only a certain aspect of the overall system. A view anticipates the (potential) behavior of the complete system by its loose semantics. This ensures that properties of the view are inherited by the complete system. Based on this result one may verify temporal properties by decomposing a specification into several views, analyzing them separately, and deriving the desired property from properties shown for the views.

Reiko Heckel and Hartmut Ehrig and Uwe Wolter and Andrea Corradini: Integrating the Specification Techniques of Graph Transformation and Temporal Logic. In Proceedings of the 22nd International Symposium on Mathematical Foundations of Computer Science (MFCS 1997), Bratislava (Slovakia). Springer (London, UK), LNCS, pp. 219--228 (1997)
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@inproceedings{Heckel1997, author = {Reiko Heckel and Hartmut Ehrig and Uwe Wolter and Andrea Corradini}, title = {Integrating the Specification Techniques of Graph Transformation and Temporal Logic}, booktitle = {Proceedings of the 22nd International Symposium on Mathematical Foundations of Computer Science (MFCS 1997), Bratislava (Slovakia)}, year = {1997}, series = {LNCS}, pages = {219--228}, address = {London, UK}, publisher = {Springer} }

The aim of this paper is an integration of graph grammars with different kinds of behavioural constraints, in particular with temporal logic constraints. Since the usual algebraic semantics of graph transformation systems is not able to express constrained behaviour we introduce - in analogy to other approaches - a coalgebraic semantics which associates with each system a category of models (deterministic transition systems). Such category has a final object, which includes all finite and infinite transition sequences. The coalgebraic framework makes it possible to introduce a general notion of 'logic of behavioural constraints'. Instances include, for example, graphical consistency constraints and temporal logic constraints. We show that the considered semantics can be restricted to a final coalgebra semantics for systems with behavioural constraints. This result can be instantiated in order to obtain a final coalgebra semantics for graph grammars with temporal logic constraints.

Gregor Engels and Reiko Heckel and Gabriele Taentzer and Hartmut Ehrig: A View-Oriented Approach to System Modelling Using Graph Transformations. In M. Jazayeri and H. Schauer (eds.): Proceedings European Software Engineering Conference (ESEC 1997), Zürich (Switzerland). Springer (Berlin/Heidelberg), vol. 1301, pp. 327-343 (1997)
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@inproceedings{Engels97, author = {Gregor Engels and Reiko Heckel and Gabriele Taentzer and Hartmut Ehrig}, editor = {M. Jazayeri and H. Schauer}, title = {A View-Oriented Approach to System Modelling Using Graph Transformations}, booktitle = {Proceedings European Software Engineering Conference (ESEC 1997), Zürich (Switzerland)}, year = {1997}, volume = {1301}, pages = {327-343}, address = {Berlin/Heidelberg}, publisher = {Springer} }

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.

Reiko Heckel: Behavioral Constraints for Loose Graph Transformation Systems. In Report on the Dagstuhl-Seminar 9637 on Graph Transformations in Computer Science. Technical University of Berlin, Dagstuhl-Seminar-Report, no. 155, pp. 12--13 (1996)
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@inproceedings{Hec96, author = {Reiko Heckel}, title = {Behavioral Constraints for Loose Graph Transformation Systems}, booktitle = {Report on the Dagstuhl-Seminar 9637 on Graph Transformations in Computer Science}, year = {1996}, number = {155}, series = {Dagstuhl-Seminar-Report}, pages = {12--13}, month = {September}, publisher = {Technical University of Berlin} }

In this lecture, the concept of synchronization of views presented at the same seminar in the framework of typed graph transformation systems with loose semantics is extended by behavioral constraints. Such constraints can be used to control the transformation process, to express properties of systems for their verification, or (what provided the initial motivation of this talk) to restrict the loose semantics of productions. Examples of behavioral constraints include starting and ending graphs, application conditions for productions, static and dynamic integrity constraints, programmed graph transformations, etc. In order to support a variety of behavioral constraints we develop a generic framework for behavioral constraints for typed graph transformation systems in the double-pushout approach. The framework, called logic of behavioral constraints, provides the main notions and results presented in the talk on synchronization of views and loose semantics of productions on an axiomatic basis. The techniques are motivated by the concepts of logic of constraints and institutions in the field of algebraic specification of abstract data types. Known instances of logics of behavioral constraints include (so far) delete/create permissions for graph transitions, negative application conditions for productions, as well as static and dynamic integrity constraints expressed by temporal logic. For any given logic of behavioral constraints, the synchronization by parallel composition of graph transformation systems as well as the transition sequence semantics extend to graph transformation systems with constraints. Moreover, the compositionality of the semantics w.r.t. the synchronization has been transfered to the extended setting. The framework can be made approach independent if we assume a category of graph transformation systems (of whatever approach) such that a morphism of that category corresponds to a translation of the transformation steps in the source system to transformation steps in the target system. Then, a flat (unstructured) graph transformation system becomes comparable to a flat GRACE transformation unit, which could provide a new way of structuring transformation units, featuring refinement and synchronization in addition to the currently available use relation.

Hartmut Ehrig and Reiko Heckel and Julia Padberg and Gabriele Taentzer and Uwe Wolter and Andrea Corradini and Gregor Engels: Synchronization of Views and Loose Semantics of Typed Graph Productions. In Report on the Dagstuhl-Seminar 9637 on Graph Transformations in Computer Science. Technical University of Berlin, no. 155, pp. 11--12 (1996)
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@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}, number = {155}, pages = {11--12}, month = {September}, publisher = {Technical University of Berlin} }

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.

Gregor Engels and Hartmut Ehrig and Reiko Heckel and Gabriele Taentzer and Andrea Corradini: A View-Based Approach to System Modelling. In Report on Dagstuhl-Seminar 9637 on Graph Transformations in Computer Science. Technical University of Berlin, Dagstuhl-Seminar-Report, vol. 155, pp. 11 (1996)
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@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}, volume = {155}, series = {Dagstuhl-Seminar-Report}, pages = {11}, month = {September}, publisher = {Technical University of Berlin} }

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).

Reiko Heckel: Embedding of Conditional Graph Transformations. In Proceedings of the Colloquium on Graph Transformation and its Application in Computer Science. Universitat de les Illes Balears, Technical Report, no. B-19 (1995)
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@inproceedings{Hec95b, author = {Reiko Heckel}, title = {Embedding of Conditional Graph Transformations}, booktitle = {Proceedings of the Colloquium on Graph Transformation and its Application in Computer Science}, year = {1995}, number = {B-19}, series = {Technical Report}, publisher = {Universitat de les Illes Balears} }

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.

Reiko Heckel and Jürgen Müller and Gabriele Taentzer and Annika Wagner: Attributed Graph Transformations with Controlled Application of Rules. In Proceedings of the Colloquium on Graph Transformation and its Application in Computer Science. Universitat de les Illes Balears, Technical Report, no. B-19 (1995)
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@inproceedings{HMTW95, author = {Reiko Heckel and Jürgen Müller and Gabriele Taentzer and Annika Wagner}, title = {Attributed Graph Transformations with Controlled Application of Rules}, booktitle = {Proceedings of the Colloquium on Graph Transformation and its Application in Computer Science}, year = {1995}, number = {B-19}, series = {Technical Report}, publisher = {Universitat de les Illes Balears} }

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.

Reiko Heckel and Marc Lohmann: Towards Contract-based Testing of Web Services. In Proceedings of the International Workshop on Test and Analysis of Component Based Systems (TACoS 2004). Elsevier, vol. 116, pp. 145--156 (2005)
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@inproceedings{Heckel2005a, author = {Reiko Heckel and Marc Lohmann}, title = {Towards Contract-based Testing of Web Services}, booktitle = {Proceedings of the International Workshop on Test and Analysis of Component Based Systems (TACoS 2004)}, year = {2005}, volume = {116}, pages = {145--156}, month = {January }, publisher = {Elsevier} }

Web Services are composed by linking together service providers and requestors. To ensure interoperability, the requestor’s requirements for a service have to be matched against a service description offered by the provider. Besides data types and operation signatures, this requires service specifications to include behavioral information, like contracts specifying pre- and post-conditions of (required or provided) operations. In this paper, we propose to visualize contracts by graph transformation rules which blend well with a UML-based notion of data models and signatures. The operational interpretation of rules could turn out to be useful for simulating the behavior of required components in unit testing.

Reiko Heckel and Sebastian Thöne: Behavioral Refinement of Graph Transformation-Based Models. In Proceedings of the workshop on Software Evolution through Transformations (SETra 2004), Rome (Italy). Elsevier (Amsterdam, The Netherlands), vol. 127, no. 3, pp. 101--111 (2005) ICGT 2004
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@inproceedings{Heckel2005, author = {Reiko Heckel and Sebastian Thöne}, title = {Behavioral Refinement of Graph Transformation-Based Models}, booktitle = {Proceedings of the workshop on Software Evolution through Transformations (SETra 2004), Rome (Italy)}, year = {2005}, volume = {127}, number = {3}, pages = {101--111}, address = {Amsterdam, The Netherlands}, publisher = {Elsevier}, note = {ICGT 2004} }

Model-driven software engineering requires the refinement of abstract models into more concrete, platform-specific ones. To create and verify such refinements, behavioral models capturing reconfiguration or communication scenarios are presented as instances of a dynamic meta-model, i.e., a typed graph transformation system specifying the concepts and basic operations scenarios may be composed of. Possible refinement relations between models can now be described based on the corresponding meta-models. In contrast to previous approaches, refinement relations on graph transformation systems are not defined as fixed syntactic mappings between abstract transformation rules and, e.g., concrete rule expressions, but allow for a more loose, semantically defined relation between the transformation systems, resulting in a more flexible notion of refinement.

Reiko Heckel and Alexey Cherchago and Marc Lohmann: A Formal Approach to Service Specification and Matching based on Graph Transformation. In Proceedings of the First International Workshop on Web Services and Formal Methods (WSFM 2004), Pisa, Italy. Elsevier, vol. 105, pp. 37--49 (2004)
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@inproceedings{Heckel2004b, author = {Reiko Heckel and Alexey Cherchago and Marc Lohmann}, title = {A Formal Approach to Service Specification and Matching based on Graph Transformation}, booktitle = {Proceedings of the First International Workshop on Web Services and Formal Methods (WSFM 2004), Pisa, Italy}, year = {2004}, volume = {105}, pages = {37--49}, month = {December }, publisher = {Elsevier} }

When Web services are composed by linking service providers and requestors, the requestor's requirements for a "useful" service have to be matched against the service description offered by the provider. Among other things, service specifications (requirements or descriptions) may contain operation contracts specifying pre-conditions and effects of (required or provided) operations. In this paper we provide a semi-formal, UML-based notation for contracts and contract matching, as well as a formalization of these notions in terms of graph transformation. We establish the desired semantic relation between requestor and provider specifications and prove the soundness of our syntactic notion of matching w.r.t. this relation.

Reiko Heckel and Sebastian Thöne: Behavior-Preserving Refinement Relations between Dynamic Software Architectures. In Proceedings of the workshop on Algebraic Development Techniques (WADT 2004), Barcelona (Spain). Springer (Berlin/Heidelberg), LNCS, vol. 3423, pp. 1--27 (2004)
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@inproceedings{Heckel2004a, author = {Reiko Heckel and Sebastian Thöne}, title = {Behavior-Preserving Refinement Relations between Dynamic Software Architectures}, booktitle = {Proceedings of the workshop on Algebraic Development Techniques (WADT 2004), Barcelona (Spain)}, year = {2004}, volume = {3423}, series = {LNCS}, pages = {1--27}, address = {Berlin/Heidelberg}, publisher = {Springer} }

In this paper, we address the refinement of abstract architectural models into more platform-specific representations. For each level of abstraction, we employ an architectural style covering structural restrictions on component configurations as well as supported communication and reconfiguration operations. Architectural styles are formalized as graph transformation systems with graph transformation rules defining the available operations. Architectural models are given as graphs to which one can directly apply the transformation rules in order to simulate operations and their effects. In addition to previous work, we include process descriptions into our architectural models in order to control the communication and reconfiguration behavior of the components. The execution semantics of these processes is also covered by graph transformation systems. We propose a notion of refinement which requires the preservation of both structure and behavior at the lower level of abstraction. Based on formal refinement relationships between abstract and platform-specific styles, we can use model checking techniques to verify that abstract scenarios can also be realized in the platform-specific architecture.

Reiko Heckel and Marc Lohmann: Towards Model-Driven Testing. In Proceedings of the workshop on Test and Analysis of Component Based Systems (TACoS 2003, satellite event of the ETAPS 2003), Warsaw (Poland). Elsevier (Amsterdam, The Netherlands), vol. 82, no. 6, pp. 33-43 (2003)
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@inproceedings{Heckel2003b, author = {Reiko Heckel and Marc Lohmann}, title = {Towards Model-Driven Testing}, booktitle = {Proceedings of the workshop on Test and Analysis of Component Based Systems (TACoS 2003, satellite event of the ETAPS 2003), Warsaw (Poland)}, year = {2003}, volume = {82}, number = {6}, pages = {33-43}, address = {Amsterdam, The Netherlands}, month = {April}, publisher = {Elsevier} }

The OMG’s Model-Driven Architecture is a strategy towards interoperability across heterogeneous middleware platforms through the reuse of platform independent designs based on the distinction of, and transformation between, platformindependent and platform-specific models. A corresponding strategy for model-driven testing requires a similar structure to facilitate, besides the generation of test cases and oracles, the execution of tests on different target platforms. In this paper, we discuss different aspects of such a strategy in a specific instance: the development of web-based distributed applications. In particular, we will be concerned with the problem of reusing platform-independent test cases and test oracles and with the generation of oracles from executable models.

Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer: Dynamic Meta Modeling with Time: Specifying the Semantics of Multimedia Sequence Diagrams. In Proceedings of the Workshop on Graph Transformation and Visual Modelling Techniques (GT-VMT 2002, satellite event of the International Conference on Graph Transformation (ICGT 2002)), Barcelona (Spain). Elsevier, Electronic Notes in Theoretical Computer Science, vol. 72, no. 3, pp. 133-144 (2003)
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@inproceedings{Hausmann2003b, author = {Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer}, title = {Dynamic Meta Modeling with Time: Specifying the Semantics of Multimedia Sequence Diagrams}, booktitle = {Proceedings of the Workshop on Graph Transformation and Visual Modelling Techniques (GT-VMT 2002, satellite event of the International Conference on Graph Transformation (ICGT 2002)), Barcelona (Spain)}, year = {2003}, volume = {72}, number = {3}, series = {Electronic Notes in Theoretical Computer Science}, pages = {133-144}, month = {October}, publisher = {Elsevier} }

The Unified Modeling Langugage (UML) offers different diagram types to model the behavior of software systems. In some domains like embedded realtime systems or multimedia systems, it is necessary to include specifications of time in behavioral models since the correctness of these applications depends on the fulfillment of temporal requirements in addition to functional requirements. UML thus already incorporates language features to model time and temporal constraints. Such model elements must have an equivalent in the semantic domain. We have proposed Dynamic Meta Modeling (DMM), an approach based on graph transformation, as a means for specifying operational semantics of dynamic UML diagrams. In this article, we extend this approach to also account for time by extending the semantic domain to timed graph transformation. This enables us to define the operational semantics of UML diagrams with time speci- fications. As an example, we provide semantics for special sequence diagrams from the domain of multimedia application modeling.

Reiko Heckel and Marc Lohmann and Sebastian Thöne: Towards a UML Profile for Service-Oriented Architectures. In Proceedings of the Workshop on Model Driven Architecture: Foundations and Applications (MDAFA 2003), Enschede (The Netherlands). University of Twente (Enschede, The Netherlands), CTIT Technical Report, vol. TR–CTIT–03–27, pp. 115--120 (2003)
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@inproceedings{HLT03MDAFA, author = {Reiko Heckel and Marc Lohmann and Sebastian Thöne}, title = {Towards a UML Profile for Service-Oriented Architectures}, booktitle = {Proceedings of the Workshop on Model Driven Architecture: Foundations and Applications (MDAFA 2003), Enschede (The Netherlands)}, year = {2003}, volume = {TR–CTIT–03–27}, series = {CTIT Technical Report}, pages = {115--120}, address = {Enschede, The Netherlands}, month = {June }, publisher = {University of Twente} }

Jan Hendrik Hausmann and Reiko Heckel and Marc Lohmann: Towards Automatic Selection of Web Services Using Graph Transformation Rules. In Proceeding of the Web Service Workshop (Berliner XML-Tage 2003), Berlin (Germany). XML-Clearinghouse, pp. 286--291 (2003)
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@inproceedings{HHL03WS, author = {Jan Hendrik Hausmann and Reiko Heckel and Marc Lohmann}, title = {Towards Automatic Selection of Web Services Using Graph Transformation Rules}, booktitle = {Proceeding of the Web Service Workshop (Berliner XML-Tage 2003), Berlin (Germany)}, year = {2003}, pages = {286--291}, publisher = {XML-Clearinghouse} }

The Web service architecture promises to be highly dynamic. The idea is that a service requester can discover a needed service at runtime. Due to the fact that this discovery process relies on a semantic understanding of the offered services, it is presently performed manually at development time only. In this paper we propose to use graph transformation rules to describe the semantics of Web services. These rules provide precise semantic specifications needed for an automated service discovery in a visual and intuitive way.

Luciano Baresi and Reiko Heckel and Sebastian Thöne and Dániel Varró: Modeling and Analysis of Architectural Styles Based on Graph Transformation. In Proceedings of the 6th ICSE Workshop on Component Based Software Engineering: Automated Reasoning and Prediction (CBSE 2003), Portland, OR (USA). Carnegie Mellon University (USA), and Monash University (Australia), pp. 67--72 (2003)
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@inproceedings{Baresi2003a, author = {Luciano Baresi and Reiko Heckel and Sebastian Thöne and Dániel Varró}, title = {Modeling and Analysis of Architectural Styles Based on Graph Transformation}, booktitle = {Proceedings of the 6th ICSE Workshop on Component Based Software Engineering: Automated Reasoning and Prediction (CBSE 2003), Portland, OR (USA)}, year = {2003}, pages = {67--72}, month = {May 3-4}, publisher = {Carnegie Mellon University (USA), and Monash University (Australia)} }

Ralph Depke and Jan Hendrik Hausmann and Reiko Heckel: Design of an Agent-Oriented Modeling Language Based on Graph Transformation. In Proceedings of the International Workshop on Applications of Graph Transformations with Industrial Relevance (AGTIVE 2003), Charlottesville, VA (USA). Springer (Berlin/Heidelberg), LNCS, vol. 3062, pp. 106--119 (2003)
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@inproceedings{Depke2003a, author = {Ralph Depke and Jan Hendrik Hausmann and Reiko Heckel}, title = {Design of an Agent-Oriented Modeling Language Based on Graph Transformation}, booktitle = {Proceedings of the International Workshop on Applications of Graph Transformations with Industrial Relevance (AGTIVE 2003), Charlottesville, VA (USA)}, year = {2003}, volume = {3062}, series = {LNCS}, pages = {106--119}, address = {Berlin/Heidelberg}, month = {September}, publisher = {Springer} }

The use of UML extension mechanisms for the definition of an Agent-Oriented Modeling Language only fixes its syntax. But agent concepts demand an appropriate semantics for a visual modeling language. Graphs have been shown to constitute a precise and general semantic domain for visual modeling languages. The question is how agent concepts can be systematically represented in the semantic domain and further on be expressed by appropriate UML diagrams. We propose a language architecture based on the semantic domain of graphs and elements of the concrete syntax of UML. We use the proposed language architecture to define parts of an agent-oriented modeling language.

Tim Schattkowsky and Marc Lohmann and Reiko Heckel: Lightweight Modeling of Dynamic Websites using UML. In Proceedings of Workshop on Web Engineering (satellite event of the ICSE 2002), Orlando, FL (USA). (2002)
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@inproceedings{Schattkowsky2002a, author = {Tim Schattkowsky and Marc Lohmann and Reiko Heckel}, title = {Lightweight Modeling of Dynamic Websites using UML}, booktitle = {Proceedings of Workshop on Web Engineering (satellite event of the ICSE 2002), Orlando, FL (USA)}, year = {2002}, month = {Mai} }

Development of small- or medium scale Web applications is usually performed by teams consisting of graphic designers responsible for the layout and software developers realizing the business logic. Due to short production cycles, these people have to work in parallel on the implementation. Because of the different backgrounds of the people involved and the relative simplicity of the application, a simple design process and modeling approach is required which supports communication between team members and helps to identify and relate their respective tasks. We propose a simple subset of the UML adapted to the problem domain by means of stereotypes. Based on the design, we propose a strategy for generating code templates specifically tailored to the tasks of each team member, so that the implementation can immediately start in parallel when the modeling is complete.

Reiko Heckel and Gregor Engels: Towards a Formal Framework for Inter-Enterprise Application Integration. In Proceedings of the Closing Workshop of the TMR Network GETGRATS (2002), Bordeaux (France). Elsevier, Electronic Notes in Theoretical Computer Science, vol. 51, pp. 139--151 (2002)
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@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}, volume = {51}, series = {Electronic Notes in Theoretical Computer Science}, pages = {139--151}, month = {Juni }, publisher = {Elsevier} }

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.

Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer: Extended Model Relations with Graphical Consistency Conditions. In Proceeding of the Workshop on Consistency Problems in UML-based Software Development (satellite event of the UML 2002), Dresden (Germany). Department of Software Engineering and Computer Science, Blekinge Institute of Technology, pp. 61--74 (2002) Research Report 2002:06
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@inproceedings{Hausmann2002a, author = {Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer}, title = {Extended Model Relations with Graphical Consistency Conditions}, booktitle = {Proceeding of the Workshop on Consistency Problems in UML-based Software Development (satellite event of the UML 2002), Dresden (Germany)}, year = {2002}, pages = {61--74}, publisher = {Department of Software Engineering and Computer Science, Blekinge Institute of Technology}, note = {Research Report 2002:06} }

Consistency of models and model transformations are strongly interrelated topics. It is thus desirable to have a single notation to express model properties concerning both aspects. When using meta modeling techniques, graph transformations are a natural candidate to express model transformations. This paper explores the use of graph transformations for denoting consistency conditions between models. This technique yields benefits for different types of interrelation between transformation and consistency. A special focus is put on the generation of automatic consistency-establishing transformations.

Reiko Heckel and Jochen Küster and Gabriele Taentzer: Towards Automatic Translation of UML Models into Semantic Domains. In Proceedings of the APPLIGRAPH Workshop on Applied Graph Transformation (AGT 2002, satellite event of the ETAPS 2002), Grenoble (France). Universität Bremen, pp. 11--21 (2002)
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@inproceedings{HKT02AGT, author = {Reiko Heckel and Jochen Küster and Gabriele Taentzer}, title = {Towards Automatic Translation of UML Models into Semantic Domains}, booktitle = {Proceedings of the APPLIGRAPH Workshop on Applied Graph Transformation (AGT 2002, satellite event of the ETAPS 2002), Grenoble (France)}, year = {2002}, pages = {11--21}, month = {April }, publisher = {Universität Bremen} }

The use of UML for software specification leads usually to lots of diagrams showing different aspects and components of the software system in several views. In order to support a view-oriented approach to system modeling, consistency views and in between views has to be manageable. It is a reasonable approach to consistency management when first chossing a suitable semantic domain, provide a partial mapping into this domain, and specity as well as verify consistency constraints formulated in that domain. Annotated meta model rules can be used to translate elements of UML models into the semantic domain chosen. In this contribution, we consider triple graph grammars and attributed graph transformation approaches for the precise definition of meta model rules an outline the tool support for automatic translation.

Szilvia Gyapay and Reiko Heckel: Towards Graph Transformation with Time. In Proceedings of the APPLIGRAPH Workshop on Application of Graph Transformation (AGT 2002, satellite event of the ETAPS 2002), Grenoble (France). Universität Bremen, pp. 131--140 (2002)
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@inproceedings{GH02AGT, author = {Szilvia Gyapay and Reiko Heckel}, title = {Towards Graph Transformation with Time}, booktitle = {Proceedings of the APPLIGRAPH Workshop on Application of Graph Transformation (AGT 2002, satellite event of the ETAPS 2002), Grenoble (France)}, year = {2002}, pages = {131--140}, month = {April }, publisher = {Universität Bremen} }

Following TER nets, an approach to the modelling of time in high-level Petri nets, we propose a model of time within (attributed) graph transformation systems where time stamps are represented as distinguished node attributes. Corresponding axioms for the time model in TER nets are generalised to graph transformation systems and semantic variations are discussed. The resulting notions of typed graph transformation with time specialise the algebraic double-pushout (DPO) approach to typed graph transformation. In particular, the concurrency theory of the DPO approach can be used in the transfer of the basic theory of TER nets.

Gregor Engels and Jochen Küster and Reiko Heckel: Towards Consistency-Preserving Model Evolution. In Proceedings of the International Workshop on Principles of Software Evolution(satellite event of the ICSE 02), Orlando, Florida (USA). ACM Press (New York, NY, USA), pp. 129--132 (2002)
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@inproceedings{Engels02, author = {Gregor Engels and Jochen Küster 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}, address = {New York, NY, USA}, month = {May}, publisher = {ACM Press} }

Reiko Heckel and Jochen Küster: Behavioral Constraints for Visual Models. In Proceeding of the Workshop on Graph Transformation and Visual Modelling Techniques (GT-VMT 2001, satellite event of the ICALP 2001), Heraklion (Greece). Elsevier, Electronic Notes in Theoretical Computer Science, vol. 50, no. 3 (2001)
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@inproceedings{Heckel2001c, author = {Reiko Heckel and Jochen Küster}, title = {Behavioral Constraints for Visual Models}, booktitle = {Proceeding of the Workshop on Graph Transformation and Visual Modelling Techniques (GT-VMT 2001, satellite event of the ICALP 2001), Heraklion (Greece)}, year = {2001}, volume = {50}, number = {3}, series = {Electronic Notes in Theoretical Computer Science}, publisher = {Elsevier} }

Ralph Depke and Reiko Heckel and Jochen Küster: Agent-oriented Modeling with Graph Transformation. In Proceedings of the First international workshop on Agent-oriented software engineering (AOSE 2000), Limerick (Ireland). Springer (Berlin/Heidelberg), LNCS, vol. 1957, pp. 105--120 (2001)
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@inproceedings{Depke2001a, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Agent-oriented Modeling with Graph Transformation}, booktitle = {Proceedings of the First international workshop on Agent-oriented software engineering (AOSE 2000), Limerick (Ireland)}, year = {2001}, volume = {1957}, series = {LNCS}, pages = {105--120}, address = {Berlin/Heidelberg}, publisher = {Springer} }

The agent paradigm can be seen as an extension of the notion of (active) objects by concepts like autonomy, cooperation, and goal-oriented behavior. Mainstream object-oriented modeling techniques do not account for these agentspecific aspects. Therefore, dedicated techniques for agent-oriented modeling are required which are based on the concepts and notations of object-oriented modeling and extend these in order to support agent-specific concepts. In this paper, an agent-oriented modeling technique is introduced which is based on UML notation. Graph transformation is used both on the level of modeling in order to capture agent-specific aspects and as the underlying formal semantics of the approach.

Reiko Heckel and Stefan Sauer: Strengthening the Semantics of UML Collaboration Diagrams. In Proceedings of the Workshop on Dynamic Behaviour in UML Models: Semantic Questions, Munich (Germany). Ludwig-Maximilians-University (Munich (Germany)), no. 0006, pp. 63--69 (2000) Tech. Report, UML 2000 Workshop
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@inproceedings{HS00b, author = {Reiko Heckel and Stefan Sauer}, title = {Strengthening the Semantics of UML Collaboration Diagrams}, booktitle = {Proceedings of the Workshop on Dynamic Behaviour in UML Models: Semantic Questions, Munich (Germany)}, year = {2000}, number = {0006}, pages = {63--69}, address = {Munich (Germany)}, month = {October}, publisher = {Ludwig-Maximilians-University}, note = {Tech. Report, UML 2000 Workshop} }

Collaboration diagrams are strengthened by interpreting collaborations as visual queries for specifying pre and postconditions of operations. The conceptual idea is formalized by means of graph transformation rules and graph processes. A proof-theoretic interpretation is given which accounts for the composition of diagrams.

Reiko Heckel and Stefan Sauer: Dynamische Metamodellierung als Methode zur Definition einer operationalen Semantik für die UML. In Proceedings of the 7th GI-Workshop GROOM. University of Koblenz-Landau, vol. 20, no. 2, pp. 43--44 (2000) Presented at 7th GI-Workshop GROOM
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@inproceedings{HS00a, author = {Reiko Heckel and Stefan Sauer}, title = {Dynamische Metamodellierung als Methode zur Definition einer operationalen Semantik für die UML}, booktitle = {Proceedings of the 7th GI-Workshop GROOM}, year = {2000}, volume = {20}, number = {2}, pages = {43--44}, month = {May }, publisher = {University of Koblenz-Landau}, note = {Presented at 7th GI-Workshop GROOM} }

Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer: Ein Konzept zur anwendungsbezogenen UML-Semantikbeschreibung durch dynamische Metamodellierung. In Proceedings of the Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objektorientierte Software-Entwicklung on Visuelle Verhaltensmodellierung verteilter und nebenläufiger Software-Systeme, Münster (Germany). (2000) Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objektorientierte Software-Entwicklung
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@inproceedings{HHS00, author = {Jan Hendrik Hausmann and Reiko Heckel and Stefan Sauer}, title = {Ein Konzept zur anwendungsbezogenen UML-Semantikbeschreibung durch dynamische Metamodellierung}, booktitle = {Proceedings of the Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objektorientierte Software-Entwicklung on Visuelle Verhaltensmodellierung verteilter und nebenläufiger Software-Systeme, Münster (Germany)}, year = {2000}, month = {November}, note = {Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objektorientierte Software-Entwicklung} }

In diesem Beitrag stellen wir eine Methode zur Spezifikation der dynamischen Semantik von UML im Sinne einer Metamodellierung vor. Die dynamische Metamodellierung verwendet dabei UMLKollaborationsdiagramme als eine dem Modellierer bekannte Notation. Diese werden durch eine Interpretation als Regeln einer graphischen operationalen Semantik (GOS) semantisch präzisiert. Die GOS-Formalisierung beruht dabei sowohl auf Konzepten von Graphtransformationen als auch dem Ansatz der Structured Operational Semantics. GOS-Regeln werden als Deduktionsregeln für die Spezifikation eines Interpreters betrachtet, der basierend auf einer Prolog-Ausführungsmaschine realisert werden soll.

Fabio Gadducci and Reiko Heckel and Manuel Koch: A Fully Abstract Model for Graph-Interpreted Temporal Logic. In Proceedings of the 6th International Workshop on Theory and Application of Graph Transformations (TAGT 1998), Paderborn (Germany). Springer (London, UK), LNCS, vol. 1764, pp. 310--322 (2000)
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@inproceedings{Gadducci2000, author = {Fabio Gadducci and Reiko Heckel and Manuel Koch}, title = {A Fully Abstract Model for Graph-Interpreted Temporal Logic}, booktitle = {Proceedings of the 6th International Workshop on Theory and Application of Graph Transformations (TAGT 1998), Paderborn (Germany)}, year = {2000}, volume = {1764}, series = {LNCS}, pages = {310--322}, address = {London, UK}, publisher = {Springer} }

Graph-interpreted temporal logic is an extension of propositional temporal logic for specifying graph transition systems (i.e., transition systems whose states are graphs). Recently, this logic has been used for the specification and compositional verification of safety and liveness properties of rule-based graph transformation systems. However, no calculus or decision procedure for this logic has been provided, which is the purpose of this paper. First we show that any sound and complete deduction calculus for propositional temporal logic is also sound and complete when interpreted on graph transition systems, that is, they have the same discriminating power like general transition systems. Then, structural properties of the state graphs are expressed by graphical constraints which interpret the propositional variables in the temporal formulas. For any such interpretation we construct a graph transition system which is typical and fully abstract. Typical here means that the constructed system satisfies a temporal formula if and only if the formula is true for all transition systems with this interpretation. By fully abstract we mean that any two states of the system that can not be distinguished by graphical constraints are equal. Thus, for a finite set of constraints we end up with a finite state transition system which is suitable for model checking.

Gregor Engels and Reiko Heckel: From Trees to Graphs: Defining the Semantics of Diagram Languages with Graph Transformation. In Proceedings of the Workshop on Graph Transformation and Visual Modeling Techniques (satellite events of the ICALP 2000), Geneva(Switzerland). Carleton Scientific, pp. 373--382 (2000)
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@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}, pages = {373--382}, month = {July}, publisher = {Carleton Scientific} }

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.

Ralph Depke and Reiko Heckel: Formalizing the Development of Agent-Based Systems Using Graph Processes. In Proceedings of the Workshop on Graph Transformation and Visual Modelling Techniques (satellite event of the ICALP 2000), Geneva (Switzerland). Carleton Scientific, pp. 419-426 (2000)
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@inproceedings{Depke2000c, author = {Ralph Depke and Reiko Heckel}, title = {Formalizing the Development of Agent-Based Systems Using Graph Processes}, booktitle = {Proceedings of the Workshop on Graph Transformation and Visual Modelling Techniques (satellite event of the ICALP 2000), Geneva (Switzerland)}, year = {2000}, pages = {419-426}, publisher = {Carleton Scientific} }

Graph processes are used in order to formalize the relation between global requirement specifications of multi-agent systems by means of message sequence charts, and implementation oriented design models where graph transformation rules specify the agent’s operations.

Ralph Depke and Reiko Heckel and Jochen Küster: Rollenbasierte Modellierung autonomer Agenten. In Proceedings of the Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objektorientierte Software-Entwicklung on Visuelle Verhaltensmodellierung verteilter und nebenläufiger Software-Systeme, Münster (Germany). Universität Münster (Münster) (2000) Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objekt-orientierte Software-Entwicklung
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@inproceedings{Depke2000b, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Rollenbasierte Modellierung autonomer Agenten}, booktitle = {Proceedings of the Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objektorientierte Software-Entwicklung on Visuelle Verhaltensmodellierung verteilter und nebenläufiger Software-Systeme, Münster (Germany)}, year = {2000}, address = {Münster}, month = {November}, publisher = {Universität Münster}, note = {Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objekt-orientierte Software-Entwicklung} }

Ein agentenorientierter Modellierungsprozeß läßt sich in drei typische Aktivitäten aufteilen: Anforderungsbeschreibung, Analyse und Entwurf. Die Anforderungen sind durch Beschreibungen der Systemfunktionen und durch beispielhafte Szenarien wichtiger Interaktionen gegeben. In der Analyse wird die Struktur von Agenten und Objekten bestimmt und den Agenten durch Protokolle Verhalten vorgegeben. Im Entwurf wird (globales) Verhalten auf lokale Operationen der Agenten und Objekte abgebildet. Problematisch ist der Übergang zwischen verschiedenen Aktivit äten des Prozesses. Wir führen ein Rollenkonzept ein, das diesen Übergang erleichtert und so den agentenorientierten Modellierungsprozeß verbessert.

Ralph Depke and Reiko Heckel and Jochen Küster: Deploying Agents in an Electronic Banking Environment. In Proceedings of the Workshop on Agents in Industry (Agents 2000; satellite event of the 4th International Conference on Autonomous Agents), Barcelona (Spain). (2000)
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@inproceedings{DHK00AgentsWS, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Deploying Agents in an Electronic Banking Environment}, booktitle = {Proceedings of the Workshop on Agents in Industry (Agents 2000; satellite event of the 4th International Conference on Autonomous Agents), Barcelona (Spain)}, year = {2000}, month = {Juni } }

In this paper, we report on the deployment of an agentbased extension to an electronic banking environment which has been developed in cooperation with a software company specializing in electronic banking solutions. During development of a prototype we made valuable experiences concerning the understanding and application of agent technology and its transition to industry. Several lessons that can be learnt from our experiences are discussed and issues of future research that enable the industrial application of agent.

Ralph Depke and Reiko Heckel and Jochen Küster: Requirement Specification and Design of Agent-Based Systems with Graph Transformation, Roles and UML. In Proceedings of the 1st International Workshop on Agent-Oriented Software Engineering (satellite event of the ICSE 2000), Limerick (Ireland). University of Limerick (Limerick, Ireland) (2000)
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@inproceedings{DHK00AOSEws, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Requirement Specification and Design of Agent-Based Systems with Graph Transformation, Roles and UML}, booktitle = {Proceedings of the 1st International Workshop on Agent-Oriented Software Engineering (satellite event of the ICSE 2000), Limerick (Ireland)}, year = {2000}, address = {Limerick, Ireland}, month = {Juni }, publisher = {University of Limerick} }

Ralph Depke and Reiko Heckel: Towards Role-based Modeling of Autonomous Agents. In Proceedings of the Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objektorientierte Software-Entwicklung on Visuelle Verhaltensmodellierung verteilter und nebenläufiger Software-Systeme, Münster (Germany). (2000) Publication not findable any more!
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@inproceedings{DH00b, author = {Ralph Depke and Reiko Heckel}, title = {Towards Role-based Modeling of Autonomous Agents}, booktitle = {Proceedings of the Workshop des Arbeitskreises GROOM der GI Fachgruppe 2.1.9 Objektorientierte Software-Entwicklung on Visuelle Verhaltensmodellierung verteilter und nebenläufiger Software-Systeme, Münster (Germany)}, year = {2000}, month = {November}, organization = {Universität Münster}, note = {Publication not findable any more!} }

Andrea Corradini and Reiko Heckel and Ugo Montanari: Graphical Operational Semantics. In Proceedings of the Workshop on Graph Transformation and Visual Modelling Techniques (satellite event of the ICALP 2000), Geneva (Switzerland). Carleton Scientific, pp. 411--418 (2000)
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@inproceedings{Corradini2000, author = {Andrea Corradini and Reiko Heckel and Ugo Montanari}, title = {Graphical Operational Semantics}, booktitle = {Proceedings of the Workshop on Graph Transformation and Visual Modelling Techniques (satellite event of the ICALP 2000), Geneva (Switzerland)}, year = {2000}, pages = {411--418}, publisher = {Carleton Scientific} }

We combine the methodology of Plotkin-style operational semantics with graph transformation concepts in order to specify the operational semantics of diagram languages. Keywords structured operational semantics, graph transformation, diagram languages 1 Introduction Structured Operational Semantics (SOS) [7] is a simple and powerful style of language specification providing a rich mathematical theory and a well-established methodology. Most of the developments in the area of process calculi are based on SOS specifications, but they have also been used in order to give semantics to concurrent programming languages such as Ada or Java. The basic idea is to represent the abstract syntax of programs as terms (abstract syntax trees) augmented with state information, and to specify, by structural induction, a labeled transition relation on these terms. This can be understood as the specification of an interpreter for the language where each syntactic construct is defined separately by ...

Reiko Heckel and Mercé Llabrés and Hartmut Ehrig and Fernando Orejas: Concurrency of Double-Pullback Graph Transitions. In Proceedings of workshop on Graph Transformation Systems (GraTra; satellite event of the ETAPS 2000), Berlin (Germany). (2000)
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@inproceedings{HLEO00, author = {Reiko Heckel and Mercé Llabrés and Hartmut Ehrig and Fernando Orejas}, title = {Concurrency of Double-Pullback Graph Transitions}, booktitle = {Proceedings of workshop on Graph Transformation Systems (GraTra; satellite event of the ETAPS 2000), Berlin (Germany)}, year = {2000}, month = {March} }

Ralph Depke and Reiko Heckel and Jochen Küster: Modeling Agent-Based Systems with Graph Transformation and UML: From Requirement Specifcation to Object-Oriented Design. In Proceedings of the workshop on Graph Transformation Systems (GraTra 2000), Berlin (Germany). (Berlin, Germany) (2000)
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@inproceedings{DHK00GraTra, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Modeling Agent-Based Systems with Graph Transformation and UML: From Requirement Specifcation to Object-Oriented Design}, booktitle = {Proceedings of the workshop on Graph Transformation Systems (GraTra 2000), Berlin (Germany)}, year = {2000}, address = {Berlin, Germany}, month = {March} }

Typed graph transformation systems are used to support an intregrated modeling of object- and agent-based systems. As requirement specification, global graph transformation rules determine the overall effect of the interaction among agents and objects while abstracting from the communication involved. On the design level they describe local autonomous operations by which agents may react to changes in their environment. Graph transformation rules are combined to story diagrams in order to describe the temporal ordering of an agent's local operations.

Gregor Engels and Reiko Heckel and Stefan Sauer: Dynamic Meta Modelling: A Graphical Approach to Operational Semantics. In 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). (1999)
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@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} }

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.

Andrea Corradini and Reiko Heckel and Ugo Montanari: From SOS Specifications to Structured Coalgebras: How to Make Bisimulation a Congruence. In Proceedings of the 2nd workshop on Coalgebraic Methods in Computer Science (CMCS 99). Elsevier (Amsterdam, The Netherlands), Electronic Notes in TCS, vol. 19, pp. 118--141 (1999)
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@inproceedings{Corradini1999a, author = {Andrea Corradini and Reiko Heckel and Ugo Montanari}, title = {From SOS Specifications to Structured Coalgebras: How to Make Bisimulation a Congruence}, booktitle = {Proceedings of the 2nd workshop on Coalgebraic Methods in Computer Science (CMCS 99)}, year = {1999}, volume = {19}, series = {Electronic Notes in TCS}, pages = {118--141}, address = {Amsterdam, The Netherlands}, publisher = {Elsevier} }

In this paper we address the issue of providing a structured coalgebra presentation of transition systems with algebraic structure on states determined by an equational specification ?. More precisely, we aim at representing such systems as coalgebras for an endofunctor on the category of ?-algebras. The systems we consider are specified by using a quite general format of SOS rules, the algebraic format, which in general does not guarantee that bisimilarity is a congruence. We first show that the structured coalgebra representation works only for systems where transitions out of complex states can be derived from transitions out of corresponding component states. This decomposition property of transitions indeed ensures that bisimilarity is a congruence. For a system not satisfying this requirement, next we propose a closure construction which adds context transitions, i.e., transitions that spontaneously embed a state into a bigger context or vice-versa. The notion of bisimulation for the enriched system coincides with the notion of dynamic bisimilarity for the original one, that is, with the coarsest bisimulation which is a congruence. This is sufficient to ensure that the structured coalgebra representation works for the systems obtained as result of the closure construction.

Andrea Corradini and Martin Große-Rhode and Reiko Heckel: An Algebra of Graph Derivations using Finite (co-) limit Double Theories. In Selected papers of the 13th International Workshop on Recent Trends in Algebraic Development Techniques (WADT 1998), Lisbon (Portugal). Springer (Berlin/Heidelberg), LNCS, vol. 1589, pp. 92--106 (1999)
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@inproceedings{Corradini1999, author = {Andrea Corradini and Martin Große-Rhode and Reiko Heckel}, title = {An Algebra of Graph Derivations using Finite (co-) limit Double Theories}, booktitle = {Selected papers of the 13th International Workshop on Recent Trends in Algebraic Development Techniques (WADT 1998), Lisbon (Portugal)}, year = {1999}, volume = {1589}, series = {LNCS}, pages = {92--106}, address = {Berlin/Heidelberg}, publisher = {Springer} }

Graph transformation systems have been introduced for the formal specification of software systems. States are thereby modeled as graphs, and computations as graph derivations according to the rules of the specification. Operations on graph derivations provide means to reason about the distribution and composition of computations. In this paper we discuss the development of an algebra of graph derivations as a descriptive model of graph transformation systems. For that purpose we use a categorical three level approach for the construction of models of computations based on structured transition systems. Categorically the algebra of graph derivations can then be characterized as a free double category with finite horizontal colimits. One of the main objectives of this paper is to show how we used algebraic techniques for the development of this formal model, in particular to obtain a clear and well structured theory. Thus it may be seen as a case study in theory design and its support by algebraic development techniques.

Reiko Heckel and Berthold Hoffmann and Peter Knirsch and Sabine Kuske: Simple Modules for Grace. In Selected papers of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany). Springer (Berlin/Heidelberg), LNCS, vol. 1764 , pp. 215-224 (1998)
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@inproceedings{Heckel1998b, author = {Reiko Heckel and Berthold Hoffmann and Peter Knirsch and Sabine Kuske}, title = {Simple Modules for Grace}, booktitle = {Selected papers of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany)}, year = {1998}, volume = {1764 }, series = {LNCS}, pages = {215-224}, address = {Berlin/Heidelberg}, publisher = {Springer} }

In this discussion paper for the GRACE consortium, we propose a simple concept for modules in GRACE that is based on a straight-forward extension of transformation units. We define the notions of graph transformations, graph transformation modules, graph transformation systems, give an interleaving semantics, and outline a syntax.

Fabio Gadducci and Reiko Heckel and Mercé Llabrés: DPO Derivations via Disconnected Rules. In Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany). (1998)
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@inproceedings{GHL98, author = {Fabio Gadducci and Reiko Heckel and Mercé Llabrés}, title = {DPO Derivations via Disconnected Rules}, booktitle = {Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany)}, year = {1998} }

Fabio Gadducci and Reiko Heckel and Manuel Koch: Model Checking Graph-Interpreted Temporal Formulas. In Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany). (Paderborn) (1998)
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@inproceedings{GHK98, author = {Fabio Gadducci and Reiko Heckel and Manuel Koch}, title = {Model Checking Graph-Interpreted Temporal Formulas}, booktitle = {Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany)}, year = {1998}, address = {Paderborn} }

Hartmut Ehrig and Gregor Engels and Reiko Heckel and Gabriele Taentzer: Classification and Comparison of Modularity Concepts for Graph Transformation Systems. In Pre-Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT '98), Paderborn (Germany). University of Paderborn, no. tr-ri-98-201, pp. 122--131 (1998)
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@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}, number = {tr-ri-98-201}, pages = {122--131}, month = {November}, publisher = {University of Paderborn} }

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.

Hartmut Ehrig and Reiko Heckel and Mercé Llabrés and Fernando Orejas and Julia Padberg and Grzegorz Rozenberg: Double-Pullback Graph Transitions: A Rule-Based Framework with Incomplete Information. In Selected papers from the 6th International Workshop on Theory and Application of Graph Transformations (TAGT 1998), Paderborn (Germany). Springer (Berlin/Heidelberg), LNCS, vol. 1764, pp. 85--102 (1998)
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@inproceedings{Ehrig2000, author = {Hartmut Ehrig and Reiko Heckel and Mercé Llabrés and Fernando Orejas and Julia Padberg and Grzegorz Rozenberg}, title = {Double-Pullback Graph Transitions: A Rule-Based Framework with Incomplete Information}, booktitle = {Selected papers from the 6th International Workshop on Theory and Application of Graph Transformations (TAGT 1998), Paderborn (Germany)}, year = {1998}, volume = {1764}, series = {LNCS}, pages = {85--102}, address = {Berlin/Heidelberg}, month = {November}, publisher = {Springer} }

Reactive systems perform their tasks through interaction with their users or with other systems (as parts of a bigger system). An essential requirement for modeling such systems is the ability to express this kind of interaction. Classical rule-based approaches like Petri nets and graph transformation are not suited for this purpose because they assume to have complete control about the state and its transformation. Therefore, in this paper we propose a general framework which extends a given rule-based approach by a loose semantics where the rules of the system (e.g., graph productions or Petri net transitions) are considered as incomplete descriptions of the transformations to be performed: they still determine the changes to the matched substructure but for the remaining part (the context) unspecified changes are possible representing the application of (unknown) rules from the environment. The framework is applied to graph transformation systems in the double-pushout approach as well as place-transition Petri nets leading, respectively, to the concepts of graph transition and open step.

Hartmut Ehrig and Reiko Heckel and Julia Padberg and Grzegorz Rozenberg: Graph Transformation and Other Rule-Based Formalisms with Incomplete Information. In Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany). (1998)
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@inproceedings{EHPR98, author = {Hartmut Ehrig and Reiko Heckel and Julia Padberg and Grzegorz Rozenberg}, title = {Graph Transformation and Other Rule-Based Formalisms with Incomplete Information}, booktitle = {Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany)}, year = {1998}, month = {November} }

A general framework is presented for extending graph transformation and other rule-based formalisms in such a way that transformations with incomplete information can be handled. This extension is motivated by the need to model the behaviour of open systems in different application areas using graph transformations and Petri nets. The following two problems are central within this general framework. 1. Characterization of transformations with incomplete information. 2. Recovery of information from incomplete transformations. A solution for these problems is presented for algebraic graph transformations and Petri nets using the new concepts of graph transitions based on double pullbacks and open nets based on autonomous actions for open places. Moreover, the problems are discussed for DNA-computing and other rule-based formalisms.

Hartmut Ehrig and Reiko Heckel and Mercé Llabrés and Fernando Orejas: Construction and Characterisation of Double-Pullback Graph Transitions. In Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany). (1998)
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@inproceedings{EHLO98, author = {Hartmut Ehrig and Reiko Heckel and Mercé Llabrés and Fernando Orejas}, title = {Construction and Characterisation of Double-Pullback Graph Transitions}, booktitle = {Proceedings of the 6th International Workshop on Theory and Application of Graph Transformation (TAGT 1998), Paderborn (Germany)}, year = {1998} }

Andrea Corradini and Martin Große-Rhode and Reiko Heckel: Structured Transition Systems as Lax Coalgebras. In Proceedings of the First Workshop on Coalgebraic Methods in Computer Science (CMCS 1998), Lisbon (Portugal). Elsevier, Electronic Notes in Theoretical Computer Science, vol. 11 (1998)
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@inproceedings{Corradini1998, author = {Andrea Corradini and Martin Große-Rhode and Reiko Heckel}, title = {Structured Transition Systems as Lax Coalgebras}, booktitle = {Proceedings of the First Workshop on Coalgebraic Methods in Computer Science (CMCS 1998), Lisbon (Portugal)}, year = {1998}, volume = {11}, series = {Electronic Notes in Theoretical Computer Science}, publisher = {Elsevier} }

This paper relates labeled transition systems and coalgebras with the motivation of comparing and combining their complementary contributions to the theory of concurrent systems. The well-known mismatch between these two notions for what concerns the morphisms is resolved by extending the coalgebraic framework by lax cohomomorphisms. Enriching both labeled transition systems and coalgebras with algebraic structure for an algebraic specification, the correspondence is lost again. This leads to the introduction of lax coalgebras, where the coalgebra structure is given by a lax homomorphism. The resulting category of lax coalgebras and lax cohomomorphisms for a suitable endofunctor is shown to be isomorphic to the category of structured transition systems, where both states and transitions form algebras. The framework is also presented on a more abstract categorical level using monads and comonads, extending the bialgebraic approach recently introduced by Turi and Plotkin.

Reiko Heckel: Compositional Development and Verification of Graph Transformation Systems Based on Views and View Integration. In Proceedings of the Workshop on the General Theory of Graph Transformation Systems (GETGRATS 1997), Bordeaux (France). (1997) Proceedings have not been published.
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@inproceedings{Hec97, author = {Reiko Heckel}, title = {Compositional Development and Verification of Graph Transformation Systems Based on Views and View Integration}, booktitle = {Proceedings of the Workshop on the General Theory of Graph Transformation Systems (GETGRATS 1997), Bordeaux (France)}, year = {1997}, month = {October }, note = {Proceedings have not been published.} }

Fabio Gadducci and Reiko Heckel: An Inductive View of Graph Transformation. In Proceedings of the 12th International Workshop on Recent Trends in Algebraic Development Techniques (WADT 1997), Tarquinia (Italy). Springer (Berlin/Heidelberg), LNCS, vol. 1376, pp. 223--237 (1997)
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@inproceedings{Gadducci1997, author = {Fabio Gadducci and Reiko Heckel}, title = {An Inductive View of Graph Transformation}, booktitle = {Proceedings of the 12th International Workshop on Recent Trends in Algebraic Development Techniques (WADT 1997), Tarquinia (Italy)}, year = {1997}, volume = {1376}, series = {LNCS}, pages = {223--237}, address = {Berlin/Heidelberg}, publisher = {Springer} }

The dynamic behavior of rule-based systems (like term rewriting systems [24], process algebras [27], and so on) can be traditionally determined in two orthogonal ways. Either operationally, in the sense that a way of embedding a rule into a state is devised, stating explicitly how the result is built: This is the role played by (the application of) a substitution in term rewriting. Or inductively, showing how to build the class of all possible reductions from a set of basic ones: For term rewriting, this is the usual definition of the rewrite relation as the minimal closure of the rewrite rules. As far as graph transformation is concerned, the operational view is by far more popular: In this paper we lay the basis for the orthogonal view. We first provide an inductive description for graphs as arrows of a freely generated dgs-monoidal category. We then apply 2-categorical techniques, already known for term and term graph rewriting [29, 7], recasting in this framework the usual description of graph transformation via double-pushout [13]

Fabio Gadducci and Reiko Heckel and Manuel Koch: Combining Graph Transformations with Temporal Logic. In Proceedings of the Workshop on the General Theory of Graph Transformation Systems (GETGRATS 1997), Bordeaux (France). (Bordeaux) (1997)
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@inproceedings{GHK97, author = {Fabio Gadducci and Reiko Heckel and Manuel Koch}, title = {Combining Graph Transformations with Temporal Logic}, booktitle = {Proceedings of the Workshop on the General Theory of Graph Transformation Systems (GETGRATS 1997), Bordeaux (France)}, year = {1997}, address = {Bordeaux}, month = {Oktober } }

Graph transformations [Roz97] are useful as a suitable specification formalism in many application areas, as for instance data base systems, object oriented systems, neural networks, or distributed systems. In all these areas, however, one of the key point beside specification is analisys: in the simplest form, the requirement that a few conditions have to be preserved, in order to guarantee the desired behavior of the transformation process and therefore the consistency of the whole system. In [HW95] graphical consistency conditions were developed to express static properties of a system within the formalism of graph transformations. Roughly, a graphical constraint is just a graph morphism, and a graph satisfies a constraint if, for each occurrence of the domain of this constraint in a given graph, also an occurrence of the codomain exists. A constructive procedure then integrates this consistency conditions in application conditions for rules, so that whenever a rule is applied, it preserves consistency wrt. the graphical constraint. This procedure was applied in [Koc96] for the proof of the isolation of data base transactions with ACID properties. There not only static properties had to be expressed, but also dynamic ones.

Fabio Gadducci and Reiko Heckel: A 2-Categorical Presentation of Distributed Graph Transformation. In Proceedings of the Workshop on the General Theory of Graph Transformation Systems (GETGRATS 1997), Bordeaux (France). (Bordeaux) (1997)
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@inproceedings{GH97, author = {Fabio Gadducci and Reiko Heckel}, title = {A 2-Categorical Presentation of Distributed Graph Transformation}, booktitle = {Proceedings of the Workshop on the General Theory of Graph Transformation Systems (GETGRATS 1997), Bordeaux (France)}, year = {1997}, address = {Bordeaux}, month = {Oktober } }

Reiko Heckel and Mirko Conrad and Gottfried Egger and Jörg Hiemer: Automatic Integration of Safety Invariants into Z Specifications. In Proceedings of the Workshop on Tools for System Development and Verifcation. Shaker Verlag (Bremen, Germany), vol. 1, pp. 70--83 (1996) BISS Monographs
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@inproceedings{Heckel1996, author = {Reiko Heckel and Mirko Conrad and Gottfried Egger and Jörg Hiemer}, title = {Automatic Integration of Safety Invariants into Z Specifications}, booktitle = {Proceedings of the Workshop on Tools for System Development and Verifcation}, year = {1996}, volume = {1}, pages = {70--83}, address = {Bremen, Germany}, month = {Juli}, publisher = {Shaker Verlag}, note = {BISS Monographs} }

This extended abstract describes a mechanism to automatically incorporate safety requirements into operational specifications written in Z. For every individual operation the global (i.e. operation independent) safety invariants are transformed into a predicate which is used to extend the original precondiction of the operation. The operation constructed this way shows the same beavior as the original one whenever its post state satisfies the invariant. Otherwise it refuses to do anything. The construction of the precondition can be carried out automatically and a corresponding tool development is in progress.

Reiko Heckel and Annika Wagner: Ensuring Consistency of Conditional Graph Grammars - A constructive Approach. In Proceedings of the Joint COMPUGRAPH/SEMAGRAPH Workshop on Graph Rewriting and Computation (SEGRAGRA 1995), Volterra (Italy). Elsevier, Electronic Notes in Theoretical Computer Science, vol. 2, pp. 118--126 (1995)
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@inproceedings{Heckel1995, author = {Reiko Heckel and Annika Wagner}, title = {Ensuring Consistency of Conditional Graph Grammars - A constructive Approach}, booktitle = {Proceedings of the Joint COMPUGRAPH/SEMAGRAPH Workshop on Graph Rewriting and Computation (SEGRAGRA 1995), Volterra (Italy)}, year = {1995}, volume = {2}, series = {Electronic Notes in Theoretical Computer Science}, pages = {118--126}, publisher = {Elsevier} }

Consistency conditions describe basic properties of graphs as e.g. the existence or uniqueness of certain elements. A graph grammar is consistent if the start graph satisfies the consistency condition and the rules preserve this property. We propose a general construction that transforms global consistency conditions into preconditions for individual rules. A so-constructed rule is applicable to a consistent graph if and only if the derived graph is consistent, too. The relevance of this result is motivated by an example specification of a safety-critical system that is, a roundabout.

Bernhard Bardohl and Roswitha Bardohl and Paulo Castro and Hartmut Ehrig and Reiko Heckel and Leila Ribeiro and Daltro Nunes and Alfio Martini: GRAPHIT: Graphical Support and Integration of Formal and Semiformal Methods for Software Specification and Development. In Proceedings of the 3rd German-Brazilian Workshop on Information Technology (1995), Berlin (Germany). Forschungszentrum Jülich GmbH, Bilateral Seminars of the International Bureau, vol. 26 (1995) Forschungszentrum Jülich GmbH, Bilateral Seminars of the International Bureau
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@inproceedings{Bardohl95, author = {Bernhard Bardohl and Roswitha Bardohl and Paulo Castro and Hartmut Ehrig and Reiko Heckel and Leila Ribeiro and Daltro Nunes and Alfio Martini}, title = {GRAPHIT: Graphical Support and Integration of Formal and Semiformal Methods for Software Specification and Development}, booktitle = {Proceedings of the 3rd German-Brazilian Workshop on Information Technology (1995), Berlin (Germany)}, year = {1995}, volume = {26}, series = {Bilateral Seminars of the International Bureau}, month = {December}, publisher = {Forschungszentrum Jülich GmbH}, note = {Forschungszentrum Jülich GmbH, Bilateral Seminars of the International Bureau} }

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.

Andrea Corradini and Reiko Heckel: A Compositional Approach to Structuring and Refinement of Typed Graph Grammars. In Proceedings of the Joint COMPUGRAPH/SEMAGRAPH Workshop on Graph Rewriting and Computation (SEGRAGRA 1995), Volterra (Italy). Elsevier, Electronic Notes in Theoretical Computer Science , vol. 2, pp. 46--55 (1995)
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@inproceedings{Corradini1995, author = {Andrea Corradini and Reiko Heckel}, title = {A Compositional Approach to Structuring and Refinement of Typed Graph Grammars}, booktitle = {Proceedings of the Joint COMPUGRAPH/SEMAGRAPH Workshop on Graph Rewriting and Computation (SEGRAGRA 1995), Volterra (Italy)}, year = {1995}, volume = {2}, series = {Electronic Notes in Theoretical Computer Science }, pages = {46--55}, month = {August}, publisher = {Elsevier} }

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.

Marc Lohmann and Leonardo Mariani and Reiko Heckel: A Model-Driven Approach to Discovery, Testing and Monitoring of Web Services. In L. Baresi, E. Di Nitto (eds.): Test and Analysis of Web Services. pp. 173--204 Springer (Berlin/Heidelberg) (2007)
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@incollection{Lohmann2007, author = {Marc Lohmann and Leonardo Mariani and Reiko Heckel}, title = {A Model-Driven Approach to Discovery, Testing and Monitoring of Web Services}, booktitle = {Test and Analysis of Web Services}, publisher = {Springer}, year = {2007}, pages = {173--204}, address = {Berlin/Heidelberg} }

Service-oriented computing is distinguished by its use of dynamic discovery and binding for the integration of services at runtime. This poses a challenge for testing, in particular, of the interaction between services. We propose a model-driven solution to address this challenge. Service descriptions are promoted from largely syntactical to behavioural specifications of services in terms of contracts (pre-conditions and effects of operations), expressed in a visual UML-like notion. Through mappings to semantic web languages and the Java Modeling Language (JML) contracts support the automatic discovery of services as well as the derivation of test cases and their execution and monitoring. We discuss an extended life cycle model for services based on the model-driven approach and illustrate its application using a model of a hotel reservation service.

Gregor Engels and Reiko Heckel and Alexey Cherchago: Flexible Interconnection of Graph Transformation Modules - A Systematic Approach. In H.-J. Kreowski, U. Montanari, F. Orejas, G. Rozenberg, G. Taentzer (eds.): Formal Methods in Software and System Modeling. Essays Dedicated to Hartmut Ehrig on the Occasion of His 60th Birthday. LNCS, , vol. 3393, pp. 38--63 Springer (Berlin/Heidelberg) (2005)
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@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}, publisher = {Springer}, year = {2005}, volume = {3393}, series = {LNCS}, pages = {38--63}, address = {Berlin/Heidelberg} }

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.

Gregor Engels and Alexander Förster and Reiko Heckel and Sebastian Thöne: Process Modeling using UML. In M. Dumas, W. van der Aalst, A. ter Hofstede (eds.): Process-Aware Information Systems. pp. 85-117 Wiley (New York, NY) (2005)
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@incollection{Engels2005, author = {Gregor Engels and Alexander Förster and Reiko Heckel and Sebastian Thöne}, title = {Process Modeling using UML}, booktitle = {Process-Aware Information Systems}, publisher = {Wiley}, year = {2005}, pages = {85-117}, address = {New York, NY} }

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.

Ralph Depke and Reiko Heckel: Modeling and Analysis of Agents' Goal-Driven Behavior Using Graph Transformation. In H.D. Ehrich, J.J. Meyer, M.D. Ryan (eds.): Objects, Agents and Features - Structuring Mechanisms for Contemporary Software. LNCS, , vol. 2975, pp. 81--97 Springer (Berlin/Heidelberg) (2003)
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@incollection{Depke2003, author = {Ralph Depke and Reiko Heckel}, title = {Modeling and Analysis of Agents' Goal-Driven Behavior Using Graph Transformation}, booktitle = {Objects, Agents and Features - Structuring Mechanisms for Contemporary Software}, publisher = {Springer}, year = {2003}, volume = {2975}, series = {LNCS}, pages = {81--97}, address = {Berlin/Heidelberg}, month = {February} }

Extending mainstream object-oriented concepts, the agent paradigm promotes the concept of goals realized by means of strategies. To account for such specific aspects, dedicated techniques for agent-oriented modelling are required which go beyond standard techniques of object-oriented modelling. In this paper, an agent-oriented modelling notation for goals and strategies is proposed. Based on graph transformation as semantic domain we show how the behavior of agents can be described in terms of goals and the strategies or communication protocols for achieving them. Model checking is used to verify, in a given situation, that a chosen strategy actually achieves its goal.

Reiko Heckel: Open Petri Nets as Semantic Model for Workflow Integration. In H. Ehrig, W. Reisig, H. Weber (eds.): Petri Net Technology for Communication-Based Systems, Advances in Petri Nets. LNCS, , vol. 2472, pp. 281--294 Springer (Berlin/Heidelberg) (2003)
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@incollection{Heckel2003a, author = {Reiko Heckel}, title = {Open Petri Nets as Semantic Model for Workflow Integration}, booktitle = {Petri Net Technology for Communication-Based Systems, Advances in Petri Nets}, publisher = {Springer}, year = {2003}, volume = {2472}, series = {LNCS}, pages = {281--294}, address = {Berlin/Heidelberg} }

The integration of workflows of different enterprises requires to resolve conceptual inconsistencies which are best dealt with using a high-level modelling language. Languages like the UML provide dedicated notations for workflow modelling (e.g., by means of activity diagrams), but due to the lack of formal semantics, only little support for detecting and resolving inconsistencies can be provided. We propose open Petri nets as a suitable semantic model for workflows spanning different enterprises, and discuss the use of this model to formalise a notion of consistent evolution.

Hartmut Ehrig and Kathrin Hoffmann and Julia Padberg and Paolo Baldan and Reiko Heckel: High-Level Net Processes. In W. Brauer, H. Ehrig, J. Karhumäki, A. Salomaa (eds.): Formal and Natural Computing: Essays Dedicated to Grzegorz Rozenberg. LNCS, , vol. 2300, pp. 191--219 Springer (Berlin/Heidelberg) (2002)
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@incollection{Ehrig2002, author = {Hartmut Ehrig and Kathrin Hoffmann and Julia Padberg and Paolo Baldan and Reiko Heckel}, title = {High-Level Net Processes}, booktitle = {Formal and Natural Computing: Essays Dedicated to Grzegorz Rozenberg}, publisher = {Springer}, year = {2002}, volume = {2300}, series = {LNCS}, pages = {191--219}, address = {Berlin/Heidelberg}, month = {February}, note = { } }

The notion of processes for low-level Petri nets based on occurrence nets is well known and it represents the basis for the study of the non-sequential behavior of Petri nets. Processes for high-level nets N are often defined as processes of the low level net Flat(N) which is obtained from N via a construction called flattening. In this paper we define high-level processes for high-level nets based on a suitable notion of high-level occurrence nets. The flattening of a high-level occurrence net is in general not a low-level occurrence net, due to so called assignment conflicts in the high-level net. The main technical result is a syntactical characterization of assignment conflicts. But the main focus of this paper is a conceptual discussion of future perspectives of high-level net processes including concurrency and data type aspects. Specifically, in the second part of the paper, we discuss possible extensions of high-level net processes, which are formally introduced for algebraic high-level nets in the first part of this paper. Of special interest are high-level processes with data type behavior, amalgamation, and other kinds of constructions, which are essential aspects for a proposed component concept for high-level nets.

Reiko Heckel and Gregor Engels and Hartmut Ehrig and Gabriele Taentzer: Classification and Comparison of Module Concepts for Graph Transformation Systems. In H. Ehrig, G. Engels, H.-J. Kreowski, G. Rozenberg (eds.): Handbook of Graph Grammars and Computing by Graph Transformations, Volume 2: Applications, Languages and Tools. , , vol. 2, pp. 669--689, chapter: 17. World Scientific (Singapore) (1999)
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@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}, publisher = {World Scientific}, year = {1999}, volume = {2}, chapter = {17}, pages = {669--689}, address = {Singapore} }

In this chapter we use a three-level approach for analyzing module concepts for graph transformation systems. Based on the observation that module architectures consist of basic specications like body or export interface and relations like the implementation relation between them, or the import relation between a client and a server module, module concepts are characterized by answering the questions 1. 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 the literature. As a reference example, a samplemodular specification of resource management in distributed operating systems is presented.

Reiko Heckel and Gregor Engels and Hartmut Ehrig and Gabriele Taentzer: A View-based Approach to System Modeling Based on Open Graph Transformation Systems. In H. Ehrig, G. Engels, H.-J. Kreowski, G. Rozenberg (eds.): Handbook of Graph Grammars and Computing by Graph Transformations, Volume 2: Applications, Languages and Tools. pp. 639--668 World Scientific (Singapore) (1999)
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@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}, publisher = {World Scientific}, year = {1999}, pages = {639--668}, address = {Singapore} }

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.

Andrea Corradini and Ugo Montanari and Francesca Rossi and Hartmut Ehrig and Reiko Heckel and Michael Löwe: Algebraic Approaches to Graph Transformation, Part I: Basic Concepts and Double Pushout Approach. In G. Rozenberg (eds.): Handbook of Graph Grammars and Computing by Graph Transformation, Volume 1: Foundations. pp. 163--245 World Scientific (Singapore) (1997)
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@incollection{CMREHL97I, author = {Andrea Corradini and Ugo Montanari and Francesca Rossi and Hartmut Ehrig and Reiko Heckel and Michael Löwe}, title = {Algebraic Approaches to Graph Transformation, Part I: Basic Concepts and Double Pushout Approach}, booktitle = {Handbook of Graph Grammars and Computing by Graph Transformation, Volume 1: Foundations}, publisher = {World Scientific}, year = {1997}, pages = {163--245}, address = {Singapore} }

The algebraic approaches to graph transformation are based on the concept of gluing of graphs, modelled by pushouts in suitable categories of graphs and graph morphisms. This allows one not only to give an explicit algebraic or set theoretical description of the constructions, but also to use concepts and results from category theory in order to build up a rich theory and to give elegant proofs even in complex situations. In this chapter we start with an overwiev of the basic notions common to the two algebraic approaches, the double-pushout (DPO) approach and the singlepushout (SPO) approach; next we present the classical theory and some recent development of the double-pushout approach. The next chapter is devoted instead to the single-pushout approach, and it is closed by a comparison between the two approaches.

Hartmut Ehrig and Reiko Heckel and Martin Korff and Michael Löwe and Leila Ribeiro and Annika Wagner and Andrea Corradini: Algebraic Approaches to Graph Transformation, Part II: Single Pushout Approach and Comparison with Double Pushout Approach. In G. Rozenberg (eds.): Handbook of Graph Grammars and Computing by Graph Transformations, Volume 1: Foundations. pp. 247--312 World Scientific (Singapore) (1997)
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@incollection{EHK+97, author = {Hartmut Ehrig and Reiko Heckel and Martin Korff and Michael Löwe and Leila Ribeiro and Annika Wagner and Andrea Corradini}, title = {Algebraic Approaches to Graph Transformation, Part II: Single Pushout Approach and Comparison with Double Pushout Approach}, booktitle = {Handbook of Graph Grammars and Computing by Graph Transformations, Volume 1: Foundations}, publisher = {World Scientific}, year = {1997}, pages = {247--312}, address = {Singapore} }

The algebraic approaches to graph transformation are based on the concept of gluing of graphs corresponding to pushouts in suitable categories of graphs and graph morphisms. This allows one to give not only an explicit algebraic or set theoretical description of the constructions but also to use concepts and results from category theory in order to build up a rich theory and to give elegant proofs even in complex situations. In the previous chapter we have presented an overview of the basic notions and problems common to the two algebraic approaches the double pushout DPO approach and the single pushout SPO approach and their solutions in the DPO approach. In this chapter we introduce the SPO approach to graph transformation and some of its main results. We study application conditions for graph productions and the transformation of more general structures than graphs in the SPO approach where similar generalizations have been or could be studied also in the DPO approach. Finally we present a detailed comparison of the DPO and the SPO approach especially concerning the solutions to the problems discussed for both approaches in the previous chapter.

Proceedings of the workshop on Software Evolution through Transformations, satellite of the ICGT 2002 conference, Barcelona (Spain). In Reiko Heckel and T. Mens and M. Wermelinger (eds.): Electronic Notes in Theoretical Computer Science , , vol. 72, no. 4 Elsevier (2002)
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@proceedings{HMW02, editor = {Reiko Heckel and T. Mens and M. Wermelinger}, title = {Proceedings of the workshop on Software Evolution through Transformations, satellite of the ICGT 2002 conference, Barcelona (Spain)}, year = {2002}, volume = {72}, number = {4}, series = {Electronic Notes in Theoretical Computer Science}, publisher = {Elsevier} }

Reiko Heckel and Mercé Llabrés and Hartmut Ehrig and Fernando Orejas: On the Concurrent Semantics of Open Graph Transformation Systems and Views. techreport, no. 215. University of Paderborn, Department of Computer Science (2000)
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@techreport{Heckel2000, author = {Reiko Heckel and Mercé Llabrés and Hartmut Ehrig and Fernando Orejas}, title = {On the Concurrent Semantics of Open Graph Transformation Systems and Views}, institution = {University of Paderborn, Department of Computer Science}, year = {2000}, type = {techreport}, number = {215}, month = {August} }

Ralph Depke and Reiko Heckel and Jochen Küster: Modeling Agent-Based Systems with Graph Transformation. techreport, no. tr-ri-00-213. University of Paderborn, Department of Computer Science (2000)
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@techreport{Depke2000d, author = {Ralph Depke and Reiko Heckel and Jochen Küster}, title = {Modeling Agent-Based Systems with Graph Transformation}, institution = {University of Paderborn, Department of Computer Science}, year = {2000}, type = {techreport}, number = {tr-ri-00-213}, month = {August} }

The agent paradigm can be seen as an extension of the notion of (active) objects by concepts like autonomy, cooperation, and goal-oriented behavior. Mainstream object-oriented modeling techniques do not account for the agent-specific aspects. Therefore, dedicated techniques for agent-oriented modeling are required which are based on the concepts and notations of object-oriented modeling and extend these in order to support agent-specific concepts. [...]

Hartmut Ehrig and Reiko Heckel and Mercé Llabrés and Fernando Orejas: Basic Properties of Double Pullback Graph Transitions. techreport, no. 99-02. Technical University of Berlin (1999)
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@techreport{Ehrig1999, author = {Hartmut Ehrig and Reiko Heckel and Mercé Llabrés and Fernando Orejas}, title = {Basic Properties of Double Pullback Graph Transitions}, institution = {Technical University of Berlin}, year = {1999}, type = {techreport}, number = {99-02} }

In this paper we study constructions and characterizations for graph transitiions based on double pullbacks (DPB-approach), that is a loose interpretation of graph productions, recently introduced in the literature to model graph transforamtions with incomplete information. first, we present a necessary and sufficient condition for the existence of a graph transition, a weak identification condition, and then we construct all DPB-transitions, via the minimal DPB-transition, when is given a rule and single and double redex. Second, we study the results concerning independence, local Church-Rosser properties and parallelism theorem in this DPB-approach.

Reiko Heckel and Hartmut Ehrig and Uwe Wolter and Andrea Corradini: Loose Semantics and Constraints for Graph Transformation Systems. techreport, no. 97-07. Technical University of Berlin (1997)
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@techreport{Heckel1997a, author = {Reiko Heckel and Hartmut Ehrig and Uwe Wolter and Andrea Corradini}, title = {Loose Semantics and Constraints for Graph Transformation Systems}, institution = {Technical University of Berlin}, year = {1997}, type = {techreport}, number = {97-07} }

The main aim of this paper is an extension of the theory of algebraic graph transformation systems by a loose semantics. For this purpose, graph transitions are introduced as a loose interpretation of graph productions. They are defined using a double pullback construction in contrast to classical graph derivations based on double-pushouts. Two characterisation results relate graph transitions to the classical double-pushout derivations and to amalgamated derivations, respectively. Moreover, a loose semantics for graph transformation systems is defined, which associates with each system a category of models (deterministic transition systems) defined as coalgebras over a suitable functor. Such category has a final object, which includes all finite and infinite transition sequences. Constraints are introduced in order to restrict the loose semantics of graph transformation systems. The coalgebraic framework makes it possible to define a general notion of logic of behavioural constraints. Instances include, for example, start graphs, application and consistency conditions, and temporal logic constraints. We show that the considered semantics can be restricted to a final coalgebra semantics for systems with behavioural constraints. Parts of the paper are submitted for publication as [HEWC97a,HEWC97b].

Reiko Heckel and Andrea Corradini and Hartmut Ehrig and Michael Löwe: Horizontal and Vertical Structuring of Typed Graph Transformation Systems. techreport, no. 96/22. Technical University of Berlin, Department of Computer Science (1996)
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@techreport{Heckel1996a, author = {Reiko Heckel and Andrea Corradini and Hartmut Ehrig and Michael Löwe}, title = {Horizontal and Vertical Structuring of Typed Graph Transformation Systems}, institution = {Technical University of Berlin, Department of Computer Science}, year = {1996}, type = {techreport}, number = {96/22} }

Mirko Conrad and Magdalena Gajewsky and Rainer Holl-Biniasz and Michael Rudolf and Jochen Demuth and Stephan Weber and Reiko Heckel and Jürgen Müller and Gabriele Taentzer and Annika Wagner: Graphische Spezifikation ausgewählter Teile von AGG - einem algebraischen Graphgrammatiksystem. techreport, no. 7. Technische Universität Berlin (1995)
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@techreport{Conrad1995, author = {Mirko Conrad and Magdalena Gajewsky and Rainer Holl-Biniasz and Michael Rudolf and Jochen Demuth and Stephan Weber and Reiko Heckel and Jürgen Müller and Gabriele Taentzer and Annika Wagner}, title = {Graphische Spezifikation ausgewählter Teile von AGG - einem algebraischen Graphgrammatiksystem}, institution = {Technische Universität Berlin}, year = {1995}, type = {techreport}, number = {7} }

Luciano Baresi and Reiko Heckel: Foundation and Applications of Graph Transformation. Tutorial at the 1st Intl. Conference on Graph Transformation, Barcelona (Spain) (2002)
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@booklet{BaresiHeckel2002Bar, author = {Luciano Baresi and Reiko Heckel}, title = {Foundation and Applications of Graph Transformation}, howpublished = {Tutorial at the 1st Intl. Conference on Graph Transformation, Barcelona (Spain)}, month = {October}, year = {2002} }

Andrea Corradini and Hartmut Ehrig and Reiko Heckel: Introduction to Graph Transformation. Tutorial at the European Joint Conferences on Theory and Practice of Software (ETAPS '98), Lisbon (Portugal) (1998)
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@booklet{Corradini98-2, author = {Andrea Corradini and Hartmut Ehrig and Reiko Heckel}, title = {Introduction to Graph Transformation}, howpublished = {Tutorial at the European Joint Conferences on Theory and Practice of Software (ETAPS '98), Lisbon (Portugal)}, month = {March }, year = {1998} }

Outline: Introduction and Historical Background. Basic Notions of the DPO Approach. Graph Grammars and Petri Nets. Parallelism and Concurrency. SPO Approach. Structured Productions and Derivations. Consistency and Application Conditions. Survey of Other Approaches and Applications.

Andrea Corradini and Hartmut Ehrig and Reiko Heckel: Algebraic Approaches. Lectures at the European School on Graph Transformation, Bremen (Germany) (1998)
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@booklet{Corradini98, author = {Andrea Corradini and Hartmut Ehrig and Reiko Heckel}, title = {Algebraic Approaches}, howpublished = {Lectures at the European School on Graph Transformation, Bremen (Germany)}, month = {March }, year = {1998} }

Reiko Heckel: Open Graph Transformation Systems: A New Approach to the Compositional Modelling of Concurrent and Reactive Systems. Type: Phd Thesis (1998)
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@phdthesis{Heckel1998, author = {Reiko Heckel}, title = {Open Graph Transformation Systems: A New Approach to the Compositional Modelling of Concurrent and Reactive Systems}, year = {1998} }

Reiko Heckel: Algebraic Graph Transformations with Application Conditions. Type: Diploma Thesis, diplomathesis (1995)
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@mastersthesis{Heckel1995a, author = {Reiko Heckel}, title = {Algebraic Graph Transformations with Application Conditions}, year = {1995}, type = {diplomathesis} }

Reiko Heckel and Jochen Küster and Nils Bandener and Baris Güldali and Isabell Jahnich and Christian Köpke and Michael Weking: Automatische Qualitätssicherung von UML Modellen. pg_papers, no. tr-ri-03-245. University of Paderborn (2003)
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@techreport{Heckel245, author = {Reiko Heckel and Jochen Küster and Nils Bandener and Baris Güldali and Isabell Jahnich and Christian Köpke and Michael Weking}, title = {Automatische Qualitätssicherung von UML Modellen}, institution = {University of Paderborn}, year = {2003}, type = {pg_papers}, number = {tr-ri-03-245}, month = {December} }

Mit unserer Consistency Workbench (ConWork) haben wir ein Framework zur Transformation von UML-Modellen geschaffen. Diese Transformationen geschehen anhand einer Regelmenge. So wird UML, welches keine formale Semantik hat, in eine Zielsprache mit einer formalen Semantik transformiert. Das Ergebnis der Transformation wird an einen Model-Checker weitergegeben, der die eigentliche Überprüfung vornimmt. Schließlich wird das Ergebnis der Überprüfung von ConWork angezeigt. Der Softwareentwickler weiß nun, ob sein Projekt konsistent ist oder nicht. Zur Zeit ist es nur möglich die Protokollkonsistenz zwischen Objekten zu überprüfen, da im Moment nur Regelmengen für die Transformation von Statecharts implementiert sind. Für die Transformation von weiteren UML-Diagrammtypen sind bereits die theoretischen Grundlagen vorhanden aber noch nicht in die Praxis umgesetzt.

Stefan Sauer and Reiko Heckel: Konferenzbericht ETAPS 2001. GI-Softwaretechnik-Trends, 21(2):28-31 (2001)
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@misc{Sauer01, author = {Stefan Sauer and Reiko Heckel}, title = {Konferenzbericht ETAPS 2001}, howpublished = {GI-Softwaretechnik-Trends, 21(2):28-31}, month = {August }, year = {2001} }

Die ETAPS-Multikonferenz 2001 (Fourth European Joint Conferences on Theory and Practice of Software) fand vom 2.-6- April 2001 in Genua statt. Das abwechslungsreiche Programm lockte über 500 Teilnehmer in die Hafenstadt an der italienischen Riviera, die einige Wochen später als Ausrichtugnsort eines G8-Gipfels international Furore machen sollte.