SPLIT AND ST BISIMULATION SEMANTICS

In this paper the notion of action atomicity is relaxed by permitting actions to be observed in the middle of their evolution. Non-atomic se mantic equivalences, based on the notion of bisimulation, are studied over stable event structures, Split(n) bisimulation equivalence (denot ed similar to(n) considers each event as composed of n phases. ST bisi mulation equivalence (denoted similar to(ST)) is a slight refinement o f similar to(2) where each ending phase is unambiguously associated to a beginning phase, We prove that, by increasing n, we get finer and f iner equivalences (i.e., similar to(n+1) subset of or equal to similar to(n)) and, moreover, that similar to(n+1) coincides with similar to( ST) over those event structures whose autoconcurrency is at most n. Th e main consequence of these results is that, for image finite event st ructures, similar to(ST) is the intersection of all the similar to(n). (C) 1995 Academic Press, Inc.