Publikationen zum Fachbereich Adaptive/Flexible Workflows

Konferenzbeiträge und Beiträge auf Workshops

• Dirk Fahland. Oclets - scenario-based modeling with Petri nets. In Giuliana Franceschinis and Karsten Wolf, editors, Proceedings of the 30th International Conference on Petri Nets and Other Models Of Concurrency, 22-26 May 2009, volume 5606 of Lecture Notes in Computer Science, Paris, France, pages 223-242, June 2009. Springer-Verlag. Note: (revised version).

  Abstract: We present a novel, operational, formal model for scenario-based modeling with Petri nets. A scenario-based model describes the system behavior in terms of partial runs, called scenarios. This paradigm has been formalized in message sequence charts (MSCs) and live sequence charts (LSCs) which are in industrial and academic use. A particular application for scenarios are process models in disaster management where system behavior has to be adapted frequently, occasionally at run-time. An operational semantics of scenarios would allow to execute and adapt such systems on a formal basis. In this paper, we present a class of Petri nets for specifying and modeling systems with scenarios and anti-scenarios. We provide an operational semantics allowing to iteratively construct partially ordered runs that satisfy a given specification. We prove the correctness of our results.

  

• Dirk Fahland, Daniel Lübke, Jan Mendling, Hajo Reijers, Barbara Weber, Matthias Weidlich, and Stefan Zugal. Declarative versus Imperative Process Modeling Languages: The Issue of Understandability. In John Krogstie, Terry Halpin, and Erik Proper, editors, Proceedings of the 14th International Conference on Exploring Modeling Methods in Systems Analysis and Design (EMMSAD'09), volume 29 of Lecture Notes in Business Information Processing, Amsterdam, The Netherlands, pages 353-366, June 2009. Springer-Verlag. Note: (to appear).

  Abstract: Advantages and shortcomings of different process modeling languages are heavily debated, both in academia and industry, but little evidence is presented to support judgements. With this paper we aim to contribute to a more rigorous, theoretical discussion of the topic by drawing a link to well-established research on program comprehension. In particular, we focus on imperative and declarative techniques of modeling a process. Cognitive research has demonstrated that imperative programs deliver sequential information much better while declarative programs offer clear insight into circumstantial information. In this paper we show that in principle this argument can be transferred to respective features of process modeling languages. Our contribution is a pair of propositions that are routed in the cognitive dimensions framework. In future research, we aim to challenge these propositions by an experiment.

  

• Dirk Fahland, Jan Mendling, Hajo Reijers, Barbara Weber, Matthias Weidlich, and Stefan Zugal. Declarative vs. Imperative Process Modeling Languages: The Issue of Maintainability. In Bela Mutschler, Roel Wieringa, and Jan Recker, editors, 1st International Workshop on Empirical Research in Business Process Management (ER-BPM'09), Ulm, Germany, pages 65-76, September 2009. Note: (LNBIP to appear).

  Abstract: The rise of interest in declarative languages for process modeling both justifies and demands empirical investigations into their presumed advantages over more traditional, imperative alternatives. Our concern in this paper is with the ease of maintaining business process models, for example due to changing performance or conformance demands. We aim to contribute to a rigorous, theoretical discussion of this topic by drawing a link to well-established research on maintainability of information artifacts.

  

• Dirk Fahland. Adaptive und Selbststabilisierende Workflows. In Malte Diehl, Henrik Lipskoch, Roland Meyer, and Christian Storm, editors, Proceedings des gemeinsamen Workshops der Graduiertenkollegs, Trustworthy Software Systems, Berlin, pages 55--56, 2008. Gito-Verlag.

• Dirk Fahland. Oclets -- Scenario-Based Modeling with Petri Nets. In Niels Lohmann and Karsten Wolf, editors, Proceedings of the 15th German Workshop on Algorithms and Tools for Petri Nets, AWPN 2008, Rostock, Germany, September 26--27, 2008, volume 380 of CEUR Workshop Proceedings, pages 1-6, September 2008. CEUR-WS.org.

  Abstract: Scenario-based specifications are used for modeling highly-complex, distributed systems in terms of partial runs (scenarios) the system shall have. But it is difficult to derive an implementing, operational model from a given set of scenarios, especially if concepts like anti-scenarios which must not occur are used. In this paper, we present a novel model for scenario-based specifications with Petri nets including anti-scenarios; we provide an operational semantics for our model.

  

• Dirk Fahland and Heiko Woith. Towards Process Models for Disaster Response. In Business Process Management Workshops, International Workshop on Process Management for Highly Dynamic and Pervasive Scenarios (PM4HDPS), co-located with 6th International Conference on Business Process Management (BPM'08), volume 17 of Lecture Notes in Business Information Processing, Milan, Italy, pages 254-265, September 2008. Springer.

  Abstract: In the immediate aftermath of a disaster routine processes, even if specifically designed for such a situation, are not enacted blindly. Actions and processes rather adapt their behavior based on observations and available information. Attempts to support these processes by technology rely on process models that faithfully capture process execution and adaptation. Based on experiences from actual disaster response settings, we propose to specify an adaptive process as a set of scenarios using a Petri net syntax. Our operational model provides an adaptation operator that synthesizes and adapts the system behavior at run-time based on the given scenarios. An example illustrates our approach.

  

• Dirk Fahland. A Formal Approach to Adaptive Processes using Scenario-based Concepts.. In Kees van Hee, Wolfgang Reisig, and Karsten Wolf, editors, Proceedings of the Workshop on Formal Approaches to Business Processes and Web Services (FABPWS'07), Siedlce, Poland, pages 71--85, June 2007. University of Podlasie.

  Abstract: The problem and need for adapting business processes and service behavior to cope with changing circumstances is identified well. Standard models for business processes still rely on a fixed process logic, the change of which is rather hard to achieve. Ad-hoc changes to a standard model are usually considered too `dangerous' as they are performed in not well-defined manner. Other models for adaptive processes deviate to some extent from established business process models. This deviation comes at the price of limited understandability and loss in analysis capabilities. We propose a model for adaptive processes based on Petri nets which have successfully been applied in modeling and analyzing business process and web services. Our operator to adapt the behavior of such models is formalized by the help of scenario-based concepts known from live-sequence charts in purely mathematical terms. This combination of concepts allows to write down the result of the adaptation rather than how adaptation shall be performed.

  

• Dirk Fahland. Modeling and Verifying Declarative Workflows. In Dagstuhl ''zehn plus eins'', Aachen, pages 135, 2007. Verlagshaus Mainz.

• Dirk Fahland. Synthesizing Petri nets from LTL specifications - An engineering approach. In Stephan Philippi and Alexander Pinl, editors, Proceedings 14.Workshop Algorithmen und Werkzeuge für Petrinetze (AWPN), Arbeitsbericht aus dem Fach Informatik, Nr. 25/2007, Universität Koblenz-Landau, D, pages 69--74, September 2007.

  Abstract: In this paper we present a pattern-based approach for synthesizing truly distributed Petri nets from a class of LTL specifications. The synthesis allows for the automatic, correct generation of humanly conceivable Petri nets, thus circumventing a manual construction of nets, or the use of Büuchi automata which are not distributed and often less intuitive to understand.

  

• Dirk Fahland. Towards Analyzing Declarative Workflows. In Jana Koehler, Marco Pistore, Amit P. Sheth, Paolo Traverso, and Martin Wirsing, editors, Autonomous and Adaptive Web Services, number 07061 of Dagstuhl Seminar Proceedings, 2007. Internationales Begegnungs- und Forschungszentrum fuer Informatik (IBFI), Schloss Dagstuhl, Germany.

  Abstract: Enacting tasks in a workflow cannot always follow a pre-defined process model. In application domains like disaster management workflows are partially specified and circumstances of their enactment change. There exist various approaches for formal workflow models that are effective in such situations, like declarative specifications instead of operational models for formalizing flexible workflow process. These powerful models leave a gap to existing techniques in the domain of workflow modeling, workflow analysis, and workflow management. In this paper we bridge this gap with a compositional mechanism for translating declarative workflow models to operational workflow models. The mechanism is of a general nature and we reveal its principles as we provide an exemplary definition for translating DecSerFlow models based on LTL to Petri nets. We then demonstrate its use in analyzing and refining declarative models.

  

Technische Berichte

• Dirk Fahland. Oclets - a formal approach to adaptive systems using scenario-based concepts. Informatik-Berichte 223, Humboldt-Universität zu Berlin, 2008.

  Abstract: Usually, a component in a distributed system has assumptions about the remaining components of the system. A change in one component might require to change other components as well. It may happen that the change has to be performed in the running system. In this paper, we propose a formal model for systems that change their behavior at run-time: An adaptive system is denoted as a set of scenarios using a Petri net syntax. Our operational model provides an adaptation operator that synthesizes and adapts the system behavior as a Petri net branching-process at run-time based on the given scenarios. We show the feasibility of our approach by the help of an example.

  

Studien- und Diplomarbeiten

• Manja Wolf. Erstellung einer modellbasierten Laufzeitumgebung für adaptive Prozesse. Diplomarbeit, Humboldt-Universität zu Berlin, September 2008.

  Abstract: Mit der vorliegenden Arbeit wird die Implementation von GRETA - Graphical Runtime EnvironmenT for Adaptive Processes vorgestellt. GRETA ist eine modellbasierte Laufzeitumgebung für dynamische, sich während des Ablaufes anpassende Prozesse. Für die Implementation wurde ein formales Begriffsgebäude aufgebaut, das auf einer noch in der Entwicklung befindlichen Theorie basiert und einen Teil dieser Theorie berücksichtigt. Die Theorie, das vereinfachte Begriffsgebäude und die dafür ausgearbeiteten Algorithmen werden vorgestellt. GRETA wurde als grafischer Editor implementiert, mit dem solche dynamischen Prozesse modelliert werden können und wurde zu einem Simulationswerkzeug erweitert. Mit GRETA ist es möglich, zukünftige Forschungsergebnisse zu der genannten Theorie zu erproben. Das Programm wurde mit dem Eclipse-Framework GMF (Graphical Modeling Framework) erstellt. In dem Dokument gibt es eine Einführung in die Konzepte und die Funktionalittät von GMF. Die für GRETA genutzten Features von GMF werden erläutert.

  

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