On the Step Branching Time Closure of Free-Choice Petri Nets

Abstract : Free-choice Petri nets constitute a non-trivial subclass of Petri nets, excelling in simplicity as well as in analyzability. Extensions of free-choice nets have been investigated and shown to be translatable back to interleaving-equivalent free-choice nets. In this paper, we investigate extensions of free-choice Petri nets up to step branching time equivalences. For extended free-choice nets, we achieve a generalization of the equivalence result by showing that an existing construction respects weak step bisimulation equivalence. The known translation for behavioral free-choice does not respect step branching time equivalences, which turns out to be a property inherent to all transformation functions from this net class into (extended) free-choice Petri nets. By analyzing the critical structures, we find two subsets of behavioral free-choice nets that are step branching time equivalent to free-choice nets. Finally, we provide a discussion concerning the actual closure of free-choice Petri nets up to step branching time equivalences.