Computing the Reveals Relation in Occurrence Nets

Stefan Haar
(INRIA and LSV, Ecole Normale Supérieure de Cachan and CNRS)
Christian Kern
(TU München)
Stefan Schwoon
(INRIA and LSV, Ecole Normale Supérieure de Cachan and CNRS)

Petri net unfoldings are a useful tool to tackle state-space explosion in verification and related tasks. Moreover, their structure allows to access directly the relations of causal precedence, concurrency, and conflict between events. Here, we explore the data structure further, to determine the following relation: event a is said to reveal event b iff the occurrence of a implies that b inevitably occurs, too, be it before, after, or concurrently with a. Knowledge of reveals facilitates in particular the analysis of partially observable systems, in the context of diagnosis, testing or verification; it can also be used to generate more concise representations of behaviours via abstractions. The reveals relation was previously introduced in the context of fault diagnosis, where it was shown that the reveals relation was decidable: for a given pair a,b in the unfolding U of a safe Petri net N, a finite prefix P of U is sufficient to decide whether or not a reveals b. In this paper, we first considerably improve the bound on |P|. We then show that there exists an efficient algorithm for computing the relation on a given prefix. We have implemented the algorithm and report on experiments.

In Giovanna D'Agostino and Salvatore La Torre: Proceedings Second International Symposium on Games, Automata, Logics and Formal Verification (GandALF 2011), Minori, Italy, 15-17th June 2011, Electronic Proceedings in Theoretical Computer Science 54, pp. 31–44.
Published: 4th June 2011.

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