Publikationen zum Fachbereich offene Workflownetze

Publikationen in Zeitschriften und B�chern

Peter Massuthe, Alexander Serebrenik, Natalia Sidorova, and Karsten Wolf. Can I find a Partner? Undecidablity of Partner Existence for Open Nets. Information Processing Letters, 108(6): 374--378, November 2008.

Peter Massuthe, Wolfgang Reisig, and Karsten Schmidt. An Operating Guideline Approach to the SOA. Annals of Mathematics, Computing & Teleinformatics, 1(3): 35-43, 2005.

Abstract: Interorganizational cooperation is more andmore organized by the paradigm of services. The serviceoriented architecture (SOA) provides a general framework for service interaction. It describes three roles, service provider, service requester, and service broker, together with the three operations publish, find, and bind. We provide a formal method based on Petri nets to model services and their cooperation. We characterize well-behaving pairs of requester's and provider's services and suggest operating guidelines as a convenient and intuitive artifact to realize publish. In our approach, the find operation reduces to a matching problem between the requester's service and the operating guideline. Binding of a requester's and a provider's service is therefore guaranteed to result in a well-behaving cooperating service. At this time, the approach is limited to acyclic Petri nets.

Wolfgang Reisig, Karsten Schmidt, and Christian Stahl. Kommunizierende Workflow-Services modellieren und analysieren. Informatik - Forschung und Entwicklung, pp 90-101, October 2005.

Abstract: Zur ad�quaten Nutzung von Workflow-Implementierungen kommunizierender Gesch�ftsprozesse werden Konzepte vorgeschlagen,die von konkreten Implementierungen abstrahieren. Auf der Basis von Petrinetzen werden unterschiedliche Varianten der Bedienbarkeit von Workflows charakterisiert und daf�r Entscheidungsalgorithmen vorgestellt. Die Angemessenheit des Ansatzes wird am Beispiel der Semantik von Komponenten der Gesch�ftsprozess-Modellierungssprache BPEL demonstriert.

Konferenzbeitr�ge und Beitr�ge auf Workshops

Wil M. P. van der Aalst, Niels Lohmann, Peter Massuthe, Christian Stahl, and Karsten Wolf. From Public Views to Private Views -- Correctness-by-Design for Services. In Marlon Dumas and Reiko Heckel, editors, Web Services and Formal Methods, Forth International Workshop, WS-FM 2007 Brisbane, Australia, September 28-29, 2007, Proceedings, volume 4937 of Lecture Notes in Computer Science, pages 139-153, 2008. Springer-Verlag.

Abstract: Service orientation is a means for integrating across diverse systems. Each resource, whether an application, system, or trading partner, can be accessed as a service. The resulting architecture, often referred to as SOA, has been an important enabler for interorganizational processes. Apart from technological issues that need to be addressed, it is important that all parties involved in such processes agree on the "rules of engagement". Therefore, we propose to use a contract that specifies the composition of the public views of all participating parties. Each party may then implement its part of the contract such that the implementation (i.e., the private view) accords with the contract. In this paper, we define a suitable notion of accordance inspired by the asynchronous nature of services. Moreover, we present several transformation rules for incrementally building a private view such that accordance with the contract is guaranteed by construction. These rules include adding internal tasks as well as the reordering of messages and are therefore much more powerful than existing correctness-preserving construction rules.

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.

Niels Lohmann. A Feature-Complete Petri Net Semantics for WS-BPEL 2.0. 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), pages 21-35, June 2007. University of Podlasie.

Abstract: We present an extension of a Petri net semantics for the Web Service Business Execution Language (WS-BPEL). This extension covers the novel activities and constructs introduced by the recent WS-BPEL 2.0 specification. Furthermore, we simplify several aspects of the Petri net semantics to allow for more compact models suited for computer-aided verification.

Karsten Schmidt. Controllability of Open Workflow Nets. In J�rg Desel and Ulrich Frank, editors, Enterprise Modelling and Information Systems Architectures, volume P-75 of Lecture Notes in Informatics (LNI), Bonn, pages 236-249, 2005. Entwicklungsmethoden f�r Informationssysteme und deren Anwendung (EMISA, RWTH Aachen), K�llen Druck+Verlag GmbH.

Daniela Weinberg and Karsten Schmidt. Reduction Rules for Interaction Graphs. In Karsten Schmidt and Christian Stahl, editors, 12. Workshop Algorithmen und Werkzeuge f�r Petrinetze (AWPN 2005), Proceedings, pages 60-65, September 2005. Humboldt-Universit�t zu Berlin.

Abstract: The internet today has grown to be more than just being a basisfor exchanging information. It steadily becomes a platform for processing business processes. Many companies distribute their service with the help of web services or integrate other web services into their own workflow. However, before a web service gets published it should be examined well. We will introduce a way of examining the controllability of a web service. We propose the interaction graph of a web service, that is modelled by an open workflow net. To verify whether such a net is controllable or not it is sufficient to construct a reduced interaction graph. We will define reduction rules that minimize the size of the graph greatly. The analysis using the interaction graph as well as the reduction rules are implemented and have been integrated into an analysis tool kit for web services.

Technische Berichte

Wil M. P. van der Aalst, Peter Massuthe, Arjan J. Mooij, Christian Stahl, and Karsten Wolf. Erratum -- Multiparty Contracts: Agreeing and Implementing Interorganizational Processes. Informatik-Berichte 213, Humboldt-Universit�t zu Berlin, June 2007.

Wil M. P. van der Aalst, Peter Massuthe, Christian Stahl, and Karsten Wolf. Multiparty Contracts: Agreeing and Implementing Interorganizational Processes. Informatik-Berichte 213, Humboldt-Universit�t zu Berlin, June 2007. Note: There is an erratum.

Abstract: A contract specifies an interorganizational process together with a distribution of responsibilities for the activities among the parties involved. In this paper, we formally show how a party can implement its part of the contract such that the implementation accords with the contract. We propose a formal notion of a contract and give a criterion for accordance between a local implementation and a contract such that, if all local implementations accord with the contract, the overall process is deadlock-free and it is always possible to terminate properly. Then, we sketch a technique for automatically checking the proposed accordance criterion. Finally, we present accordance-preserving transformation rules. These rules can be used to implement a part of the contract while preserving the accordance criterion.

Peter Massuthe, Wolfgang Reisig, and Karsten Schmidt. An Operating Guideline Approach to the SOA. Informatik-Berichte 191, Humboldt-Universit�t zu Berlin, 2005.

Abstract: Interorganizational cooperation is more and more organized by the paradigm of services. The service-oriented architecture (SOA) provides a general framework for service interaction. It describes three roles, service provider, service requester, and service broker, together with the three operations publish, find, and bind. We provide a formal method based on Petri nets to model services and their cooperation. We characterize well-behaving pairs of requester?s and provider?s services and suggest operating guidelines as a convenient and intuitive artifact to realize publish. Then, the find operation reduces to a matching problem between the requester?s service and the operating guideline. Binding of a requester?s and a provider?s service is therefore guaranteed to result in a well-behaving cooperating service.

Wolfgang Reisig, Karsten Schmidt, and Christian Stahl. Verteilte Gesch�ftsprozesse modellieren und analysieren. Informatik-Berichte 182, Humboldt-Universit�t zu Berlin, February 2005.

Abstract: Verteilte Gesch�ftsprozesse nutzen das Internet, um auf heterogenen Rechnerstrukturen Dienste auszubieten. Modellierungstechniken und Implementierungssprachen f�r solche Dienste werfen im Vergleich mit herk�mmlichen Rechnern grundlegend neue Fragestellungen auf. Wir diskutieren einige davon und zeigen, wie Petrinetze ihre Beantwortung erm�glichen.

Studien- und Diplomarbeiten

Patrick K�hnen. Synthese offener Workflownetze aus Serviceautomaten. Diplomarbeit, Humboldt-Universit�t zu Berlin, January 2008.

Abstract: Das Paradigma der service-orientierten Architektur beschreibt eine Kapselung einzelner Funktionalit�ten von Softwaresystemen in Services. Ein Service besitzt somit eine bestimmte Funktionalit�t und zudem eine definierte Schnittstelle. �ber diese Schnittstelle kann die Funktionalit�t des Services genutzt werden. Durch diese Trennung von Funktionalit�t und Schnittstelle ist ein Service unabh�ngig von der Plattform und der verwendeten Programmiersprache. �nderungen und Erweiterungen service-basierter Softwaresysteme k�nnen durch Anpassungen oder das Austauschen des betreffenden Services erreicht werden und sind daher im Vergleich zu anderen Systemen einfacher, schneller und mit einem geringeren Risiko umsetzbar. Web Services sind eine spezielle und weit verbreitete Form von Services. Ein Web Service ist ein eigenst�ndiges Softwaremodul, dessen Funktionalit�t �ber das Internet angeboten wird. Mit der Web Service Business Process Execution Language (WS-BPEL) kann ein Web Service definiert werden, der den Gesch�ftsprozess eines Unternehmens abbildet. WS-BPEL besitzt hierf�r Konstrollstrukturen und Funktionalit�t zur Behandlung von Fehlern und Ausnahmen. WS-BPEL besitzt keine formale Semantik und kann daher nicht formal analysiert werden. F�r eine formale Analyse kann ein WS-BPEL Prozess in ein offenes Workflownetz (oWFN) �bersetzt werden. Existiert f�r ein oWFN ein Partner, der verklemmungsfrei mit diesem oWFN interagiert, kann ein Serviceautomat (SVA) berechnet werden, der das Verhalten dieses Partners beschreibt. Bisher war es m�glich, ein oWFN nach WS-BPEL zu �bersetzen, aber nicht, ein oWFN aus einem SVA zu synthetisieren. Ein berechneter Partner f�r einen WS-BPEL Prozess in Form eines SVAs konnte somit bisher nicht zur�ck in WS-BPEL �bersetzt werden. Das Ziel dieser Arbeit ist es, die Synthese eines oWFNS aus einem SVA zu definieren und somit den Vorgang der Berechnung eines Partners f�r einen WS-BPEL Prozesss zu vervollst�ndigen.

Christian Gierds. Ein sch�rferes Kriterium f�r die Wahl von Endzust�nden in Bedienungsanleitungen, Liberalsten Partnern und Public Views. Studienarbeit, Humboldt-Universit�t zu Berlin, October 2007.

Abstract: In der Welt der Service Orientierten Architektur (SOA) besteht der Bedarf, Dienste auf ihre m�gliche Interaktion mit anderen Diensten hin zu untersuchen. Dienste werden wir in Form von Serviceautomaten betrachten, die als asynchron kommunizierende Automaten definiert sind. Um die Frage einer sinnvollen, also verklemmungsfreien Kommunikation zu kl�ren, gibt es das Konzept der Bedienungsanleitungen. Wie werden f�r diese ein scharfes Kriterium f�r die Wahl der Endzust�nde angeben und zeigen, dass diese Wahl sich in vorhandene Konzepte integriert. Besonderes Augenmerk werden wir dabei auf den Liberalsten Partner und den Public View eines Serviceautomaten werfen und an diesen unsere Definition rechtfertigen.

Gerrit M�ller. Strukturelle Analyse von offenen Workflow-Netzen hinsichtlich Bedienbarkeit. Studienarbeit, Humboldt-Universit�t zu Berlin, January 2007.
Alexander Schulz. Zielgerichtete Strategien. Studienarbeit, Humboldt-Universit�t zu Berlin, July 2007.

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