Locality and True-concurrency in Calculi for Mobile Processes

Process algebra semantics can be categorised into true-concurrency semantics, where parallel composition is considered a primitive operator, and interleaving semantics, where concurrency is reduced to sequentiality plus non-determinism. The former have an appealing intuitive justiication, but the latter are mathematically more tractable. This paper addresses the study of true-concurrency semantics in the framework of process algebras for mobile systems, like-calculus MPW92, Mil91]. We focus on location bisimulation (`), in our opinion one of the most convincing true-concurrency equivalences, which aims to describe the spatial dependencies on processes. Our main contribution is to show that in-calculus`can be expressed , or implemented, within the ordinary interleaving observation equivalence Mil89, MPW92] by means of a fairly simple and fully abstract encoding. Thus, we can take advantage of the easier theory of observation equivalence to reason about`. We illustrate this with a few examples, including the proof of the congruence properties of`. We show that in-calculusìs not a congruence, and that the full abstraction of the encoding extends to the induced congruence. The results in the paper also shed more light on the expressive power of-calculus.