The structured phase of concurrency

This extended abstract summarizes the state-of-the-art solution to the structuring problem for models that describe existing real world or envisioned processes. Special attention is devoted to models that allow for the true concurrency semantics. Given a model of a process, the structuring problem deals with answering the question of whether there exists another model that describes the process and is solely composed of structured patterns, such as sequence, selection, option for simultaneous execution, and iteration. Methods and techniques for structuring developed by academia as well as products and standards proposed by industry are discussed. Expectations and recommendations on the future advancements of the structuring problem are suggested

APQL: A process-model query language

As business process management technology matures, organisations acquire more and more business process models. The management of the resulting collections of process models poses real challenges. One of these challenges concerns model retrieval where support should be provided for the formulation and efficient execution of business process model queries. As queries based on only structural information cannot deal with all querying requirements in practice, there should be support for queries that require knowledge of process model semantics. In this paper we formally define a process model query language that is based on semantic relationships between tasks in process models and is independent of any particular process modelling notation

An efficient algorithm for the parallel solution of high-dimensional differential equations

The study of high-dimensional differential equations is challenging and difficult due to the analytical and computational intractability. Here, we improve the speed of waveform relaxation (WR), a method to simulate high-dimensional differential-algebraic equations. This new method termed adaptive waveform relaxation (AWR) is tested on a communication network example. Further we propose different heuristics for computing graph partitions tailored to adaptive waveform relaxation. We find that AWR coupled with appropriate graph partitioning methods provides a speedup by a factor between 3 and 16

Processus de branchement des réseaux de Petri à reset arcs

National audienceLes réseaux de Petri sont un outil très répandu de modélisation et d'étude des systèmes concur-rents autour desquels s'est constituée une large communauté scientifique. Il existe des extensions qui ont pour but d'étendre le formalisme de référence par les réseaux de Petri pour proposer soit des mo-dèles plus compacts en termes de description, soit plus puissants en termes de pouvoir d'expression. Nous pouvons citer entre autre l'ajout des reset arcs qui ajoutent un pouvoir expressif utile en ce sens qu'ils permettent de remettre à zéro (notion de réinitialisation) le contenu d'une place sans impacter sur les règles de sensibilisation des transitions dans le réseau. Nous proposons pour les réseaux de Petri à reset arcs ayant un réseau normal sous-jacent borné, une approche pour construire le dépliage (méthode d'ordre partiel pour contourner le problème d'explosion combinatoire lié à la construction du graphe d'états) et d'un préfixe complet et fini du dépliage. Nous présenterons aussi un algorithme pour l'identification des processus de branchement issus d'un tel dépliage

Unfolding Shape Graphs

Shape graphs have been introduced in [Ren04a, Ren04b] as an abstraction to be used in model checking object oriented software, where states of the system are represented as graphs. Intuitively, the graphs modeling the states represent the structure of objects dynamically allocated in the heap. State transitions are then generated by applying graph transformation rules corresponding to the statements of the program. Since the state space of such systems is potentially unbounded, the graphs representing the states are abstracted by shape graphs. Graph transformation systems may be analyzed [BCK01, BK02] by constructing finite structures that approximate their behaviour with arbitrary accuracy, by using techniques developed in the context of Petri nets. The approach of [BK02] is to construct a chain of finite under-approximations of the Winskel’s style unfolding of a graph grammar, as well as a chain of finite over-approximations of the unfolding, where both chains converge to the full unfolding. The approximations may then be used to check properties of the underlying graph transformation system. We apply this technique to approximate the behaviour of systems represented by shape graphs and graph tranformation rules