Ekkart Kindler

The Petri net markup language: concepts, technology, and tools

The Petri Net Markup Language (PNML) is an XML-based interchange format for Petri nets. In order to support different versions of Petri nets and, in particular, future versions of Petri nets, PNML allows the definition of Petri net types. Due to this flexibility, PNML is a starting point for a standard interchange format for Petri nets. This paper discusses the design principles, the basic concepts, and the underlying XML technology of PNML. The main purpose of this paper is to disseminate the ideas of PNML and to stimulate discussion on and contributions to a standard Petri net interchange format.

The Petri Net Markup Language

The Petri Net Markup Language (PNML) is an XML-based interchange format for Petri nets. PNML supports any version of Petri net since new Petri net types can be defined by so-called Petri Net Type Definitions (PNTD).

Process mining : A two-step approach to balance between underfitting and overfitting

Process mining includes the automated discovery of processes from event logs. Based on observed events (e.g., activities being executed or messages being exchanged) a process model is constructed. One of the essential problems in process mining is that one cannot assume to have seen all possible behavior. At best, one has seen a representative subset. Therefore, classical synthesis techniques are not suitable as they aim at finding a model that is able to exactly reproduce the log. Existing process mining techniques try to avoid such “overfitting” by generalizing the model to allow for more behavior. This generalization is often driven by the representation language and very crude assumptions about completeness. As a result, parts of the model are “overfitting” (allow only for what has actually been observed) while other parts may be “underfitting” (allow for much more behavior without strong support for it). None of the existing techniques enables the user to control the balance between “overfitting” and “underfitting”. To address this, we propose a two-step approach. First, using a configurable approach, a transition system is constructed. Then, using the “theory of regions”, the model is synthesized. The approach has been implemented in the context of ProM and overcomes many of the limitations of traditional approaches.

On the semantics of EPCs: resolving the vicious circle

One of the most debatable features of Event driven Process Chains (EPCs) is their non-local semantics. It can be shown that a single transition relation cannot precisely capture the non-local semantic of EPCs. Therefore, we formalize the non-local semantics of EPCs as a pair of two corresponding transition relations.Actually, there are different proposals for non-local semantics of EPCs. The technique proposed in this paper can be used for formalizing all kinds of non-local semantics. This way, it can be considered as a framework for defining non-local semantics and for resolving the vicious circle inherent to non-local semantics of EPCs.

Inter-operability of Workflow Applications: Local Criteria for Global Soundness

Automatic analysis techniques for business processes are crucial for todays workflow applications. Since business processes are rapidly changing, only fully automatic techniques can detect processes which might cause deadlocks or congestion. Analyzing a complete workflow application, however, is much too complex to be performed fully automatically. Therefore, techniques for analyzing single processes in isolation and corresponding soundness criteria have been proposed. Though these techniques may detect errors such as deadlocks or congestion, problems arising from an incorrect inter-operation with other processes are completely ignored. The situation becomes even worse for cross-organizational workflow applications, where some processes are not even available for analysis due to confidentiality reasons. We propose a technique which allows to detect but a few errors of workflow applications which arise from incorrect inter-operation of workflows. To this end, the dynamics of the inter-operation of different workflows must be specified by the help of sequence diagrams. Then, each single workflow can be checked for local soundness with respect to this specification. If each single workflow is locally sound, a composition theorem guarantees global soundness of the complete workflow application. This way, each organization can check its own workflows without knowing the workflows of other organizations--still global soundness is guaranteed.

A Compositional Partial Order Semantics for Petri Net Components

In this paper we introduce the concept of a Petri net component and show how systems can be composed from components. A component communicates with its environment via distinguished input and output places, which formalizes communication by message passing. Then, we present a compositional semantics for components. The semantics is an extension of processes for place/transition systems (partial order semantics). We show that the semantics is fully abstract with respect to the behaviour of closed components (essentially, processes of place/transition systems). A main feature of the compositional semantics is that composition of components corresponds to conjunction. This feature makes the compositional semantics applicable in combination with a temporal logic, which then allows to reason about systems in a compositional way. This is demonstrated by help of a simple temporal logic.

On the semantics of EPCs: A framework for resolving the vicious circle

One of the most debatable features of Event driven Process Chains (EPCs) is their non-local semantics. Most non-local semantics for EPCs either have a formal flaw or no formal definition is given at all.

Comparing relational model transformation technologies: implementing Query/View/Transformation with Triple Graph Grammars

The Model Driven Architecture (MDA) is an approach to develop software based on different models. There are separate models for the business logic and for platform specific details. Moreover, code can be generated automatically from these models. This makes transforma- tions a core technology for MDA and for model-based software engineering approaches in general. Query/View/Transformation (QVT) is the transformation technology recently proposed for this purpose by the OMG. Triple Graph Grammars (TGGs) are another transformation technology proposed in the mid-nineties, used for example in the FUJABA CASE tool. In contrast to many other transformation technologies, both QVT and TGGs declaratively define the relation between two models. With this definition, a transformation engine can execute a transformation in either direction and, based on the same definition, can also propagate changes from one model to the other. In this paper, we compare the concepts of the declarative languages of QVT and TGGs. It turns out that TGGs and declarative QVT have many concepts in common. In fact, QVT-Core can be mapped to TGGs. We show that QVT-Core can be implemented by transforming QVT-Core mappings to TGG rules, which can then be executed by a TGG transformation engine that performs the actual QVT transformation. Furthermore, we discuss an approach for mapping QVT-Relations to TGGs. Based on the semantics of TGGs, we clarify semantic gaps that we identified in the declarative languages of QVT and, furthermore, we show how TGGs can benefit from the concepts of QVT.

Reconciling TGGs with QVT

The Model Driven Architecture (MDA) is an approach to develop software based on different models. There are separate models for the business logic and for platform specific details. Moreover, code can be generated automatically from these models. This makes transformations a core technology for MDA. QVT (Query/View/Transformation) is the transformation technology recently proposed for this purpose by the OMG. TGGs (Triple Graph Grammars) are another transformation technology proposed in the mid-nineties, used for example in the FUJABA CASE tool. In contrast to many other transformation technologies, both QVT and TGGs declaratively define the relation between two models. With this relation definition, a transformation engine can execute a transformation in both directions and, based on the same definition, can also propagate changes from one model to the other. In this paper, we compare the concepts of QVT and TGGs. It turns out that TGGs and QVT have many concepts in common. In fact, fundamental parts of QVT-Core can be implemented by a TGG transformation engine. Moreover, we discuss how both technologies could profit from each other.

The Petri Net Kernel An infrastructure for building Petri net tools

Abstract.The Petri Net Kernel is an infrastructure for building Petri net tools. It relieves the programmer of a Petri net tool from implementing standard operations on Petri nets and a graphical user interface. In this paper, we discuss the motivation, the concepts, and the implementation of the Petri Net Kernel.