The pi calculus holds the promise of compile-time checks for whether a given program will have the correct interactive behaviour. The theory behind such checks is called bisimulation. In the synchronous pi calculus, it is well-known that the various natural definitions of (strong) bisimulation

algorithm for distributed memory settings using message passing communication. By using message passing, the same implementation can be used on both clusters of workstations and large shared memory machines. The algorithm performs reduction of large labeled transition systems modulo strong bisimulation. We

of external actions a certain class of systems may perform, then A := A . [ fg. Systems in that class are then represented by labelled transition systems over A and a set of predicates P . The variant of bisimulation equivalence that treats just like any action of A is called strong bisimulation

actions) and the usual laws for strong congruence. WC also establish that for sequential processes observation equivalence is not preserved under refinement of actions, whereas branching bisimulation is. For a large class of processes, it turns out that branching bisimulation and observation equivalence

indexed by distinctions-i.e., assumptions of inequality among names. These theories are based upon a semantics in terms of a labeled transition system and a notion of strong bisimulation, both of which are expounded in detail in a companion paper. We also report briefly on work-in-progress based upon

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from Petri nets) and labelled event structures are considered. On transition systems the abstract definition readily specialises to Milner's strong bisimulation. On event structures it explains and leads to a revision of history-preserving bisimulation of Rabinovitch and Traktenbrot, Goltz

it possible to present ACP c in a concise and intuitively clear way, and to bring the notion of splitting bisimulation equivalence and the issue of condition evaluation in process algebras with conditional expressions to the forefront. 1

This paper is concerned with bisimulation relations which do not only require related agents to simulate each others behavior in the direction of the arrows, but also to simulate each other when going back in history. First it is demonstrated that the back and forth variant of strong bisimulation

Petri nets) and labelled event structures are considered. On transition systems the abstract definition readily specialises to Milner's strong bisimulation. On event structures it explains and leads to a revision of history-preserving bisimulation of Rabinovitch and Traktenbrot, Goltz and van