Abstract not found

Abstract: Bisimulations in general are a powerful concept to minimize large finite state systems regarding some well-defined observational behavior. In contrast to strong bisimulation, for branching bisimulation there are only tools available that work on an explicit state space representation. In this work we present for the first time a symbolic approach for branching bisimulation that uses BDDs as basic data structure and that is based on the concept of signature refinement. First experimental results for problem instances derived from process algebraic system descriptions show the feasibility and the robustness of our approach. 1

Abstract. We show that timed branching bisimilarity as defined by van der Zwaag [14] and Baeten & Middelburg [2] is not an equivalence relation, in case of a dense time domain. We propose an adaptation based on van der Zwaag’s definition, and prove that the resulting timed branching bisimilarity is an equivalence indeed. Furthermore, we prove that in case of a discrete time domain, van der Zwaag’s definition and our adaptation coincide. 1

We develop a theory for net components with labeled interface places and transitions. Nets are shown to be isomorphic to algebraic terms, with marked places and transitions as atoms and arc addition, fusion and relabeling as operators. Net terms with the step firing rule are given a Plotkin-style SOS semantics, yielding compositionality of the operators. Some rules for reducing nets modulo strong and branching bisimilarity are given. 1

Groote and Luttik (1998a) proved that the extension of the theory pCRL with the axioms for branching bisimulation of Van Glabbeek and Weijland (1996) yields a ground complete axiomatisation of branching bisimulation algebras with data, and conditionals and alternative quantification over these, provided that the data part has built-in equality and built-in Skolem functions. In this paper we shall use this result to obtain ground complete axiomatisations of #-bisimulation algebras, delay bisimulation algebras and weak bisimulation algebras with data, conditionals and alternative quantification over data, under the same proviso as before. 1991 Mathematics Subject Classification: 03G25; 08A70; 68Q65; 68Q70 1991 Computing Reviews Classification System: D.1.3; F.1.1; F.4.1 Keywords and Phrases: Generalised Algebra, Process Algebra, Algebraic Specification, Alternative Quantification, Input Prefixing, Weak Bisimulation, Silent Step, Abstraction. Note: Research supported by the Netherlands...

Inheritance is one of the key issues of object-orientation. The inheritance mechanism allows for the definition of a subclass which inherits the features of a specific superclass. When adapting a workflow process definition to specific needs (ad-hoc change) or changing the structure of the workflow process as a result of reengineering efforts (evolutionary change), inheritance concepts are useful to check whether the new workflow process inherits some desirable properties of the old workflow process. Today's workflow management systems have problems dealing with both ad-hoc changes and evolutionary changes. As a result, a workflow management system is not used to support dynamically changing workflow processes or the workflow processes are supported in a rigid manner, i.e., changes are not allowed or handled outside of the workflow management system. In this paper, we propose inheritance-preserving transformation rules for workflow processes and show that these rules can be used to avo...

The paper is concerned with P/T nets with labeled and unlabeled places and transitions. An equivalence relation is defined for such nets, which abstracts from unlabeled nodes, generalizes place bisimilarity, preserves their branching structure and is a congruence for merge, relabeling, synchronization and refinement. The relation becomes a state-oriented one when all transitions are unlabeled and an event-oriented one when places are unlabeled.

... This paper studies various types of normed simulations. In a normed simulation, each step in a lower-level specification can be simulated by at most one step in the higher-level one, for any related pair of states. In earlier work we demonstrated that normed simulations are quite useful as a vehicle for the formalization of refinement proofs via theorem provers. Here we show that normed simulations also have pleasant theoretical properties: (1) under some reasonable assumptions, it is decidable whether a given relation is a normed forward simulation, provided tautology checking is decidable for the underlying logic; (2) at the semantic level, normed forward and backward simulations together form a complete proof method for establishing behavior inclusion, provided that the higher-level specification has finite invisible nondeterminism

We present a new distributed algorithm for state space minimization modulo branching bisimulation. Like its predecessor it uses signatures for refinement, but the refinement process and the signatures have been optimized to exploit the fact that the input graph contains no τ-loops. The optimization in the refinement process is meant to reduce both the number of iterations needed and the memory requirements. In the former case we cannot prove that there is an improvement, but our experiments show that in many cases the number of iterations is smaller. In the latter case, we can prove that the worst case memory use of the new algorithm is linear in the size of the state space, whereas the old algorithm has a quadratic upper bound. The paper includes a proof of correctness of the new algorithm and the results of a number of experiments that compare the performance of the old and the new algorithms. 1

Abstract. We consider the relational characterisation of branching bisimilarity with explicit divergence. We prove that it is an equivalence and that it coincides with the original definition of branching bisimilarity with explicit divergence in terms of coloured traces. We also establish a correspondence with several variants of an action-based modal logic with until- and divergence modalities. 1.