Master index

Pla general, del mural ceràmic que decora una de les parets del vestíbul de la Facultat de Química de la UB. El mural representa diversos símbols relacionats amb la química

Property-preserving subnet reductions for designing manufacturing systems with shared resources

AbstractThis paper handles two problems in manufacturing system design: resource sharing and system abstraction. In a manufacturing system, resources such as robots, machines, etc. are shared by several processes. When the resources are switched from one process to another, they may need some modifications such as cleaning oil, adding equipments and so on. Previous designing methods assume that the resources have no intermediate modifications. Hence, they need to be extended to handle such kinds of resource-sharing problems. As for abstraction, modeling operations with single places in manufacturing system design is very popular. From the viewpoint of verification, the objective is to verify whether the reduced model has the same desirable properties as the original one. This paper presents three kinds of property-preserving subnet reduction methods. For each reduction method, conditions are presented for ensuring that the properties liveness, boundedness and reversibility are preserved. Applications of these reduction methods to handling the above resource sharing and system abstraction problems are illustrated with an example from the manufacturing system

On Deadlockability, Liveness and Reversibility in Subclasses of Weighted Petri Nets

International audienceLiveness, (non-)deadlockability and reversibility are behavioral properties of Petri nets that are fundamental for many real-world systems. Such properties are often required to be mono-tonic, meaning preserved upon any increase of the marking. However, their checking is intractable in general and their monotonicity is not always satisfied. To simplify the analysis of these features, structural approaches have been fruitfully exploited in particular subclasses of Petri nets, deriving the behavior from the underlying graph and the initial marking only, often in polynomial time. In this paper, we further develop these efficient structural methods to analyze deadlockability, live-ness, reversibility and their monotonicity in weighted Petri nets. We focus on the join-free subclass, which forbids synchronizations, and on the homogeneous asymmetric-choice subclass, which allows conflicts and synchronizations in a restricted fashion. For the join-free nets, we provide several structural conditions for checking liveness, (non-)deadlock-ability, reversibility and their monotonicity. Some of these methods operate in polynomial time. Furthermore , in this class, we show that liveness, non-deadlockability and reversibility, taken together or separately, are not always monotonic, even under the assumptions of structural boundedness and structural liveness. These facts delineate more sharply the frontier between monotonicity and non-monotonicity of the behavior in weighted Petri nets, present already in the join-free subclass. In addition, we use part of this new material to correct a flaw in the proof of a previous characterization of monotonic liveness and boundedness for homogeneous asymmetric-choice nets, published in 2004 and left unnoticed

Third Workshop on Modelling of Objects, Components, and Agents

This booklet contains the proceedings of the Third International Workshop on Modelling of Objects, Components, and Agents (MOCA'04), October 11-13, 2004. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark and the "Theoretical Foundations of Computer Science" group at the University of Hamburg. The home page of the workshop is: http://www.daimi.au.dk/CPnets/workshop0