CCS without 's with Built{in Service Rendezvous

1. Abstract We introduce a pure process calculus and a value{passing process calculus in which the discipline of process interaction is not, as usual, the synchronous execution of actions but the service rendezvous (rendezvous). New is the following combination: (1) The rendezvous is a primitive. I.e. every particular rendezvous requires exactly one explicit synchronization between the processes taking part in it, namely at its beginning. In this way the framework to be presented here reeects the situation prevailing in many programming languages where the rendezvous is built{in. Such languages are Ada ((DoD83]), Egger's AP ((Egg91]), and POOL ((Ame87]). (2) There is no operator for sequential composition. As a consequence the value passing calculus can be deened in a way so that it is as integrated as, for example, value{passing CCS. In earlier accounts of the rendezvous to which (1) applies we have the situation that (2) does not. The non{pure formalisms in these frameworks exhibit a division between behaviour expressions and environments. I.e. they are less integrated than the value passing calculus. As notions of behavioural equivalence we propose De Nicola/Hennessy style may{ and must{equivalence. On this basis we can prove that the pure process calculus is an extension of De Nicola and Hennessy's CCS without 's. 2. Introduction For a start let us brieey recall what in principle makes up the rendezvous discipline: Every particular rendezvous is an interaction between a client process (client) and a server process (server). It is initiated by that the two processes synchronize themselves in a request and an ooer for a service to be provided by the server. Just after the synchronization the client is in a wait state. It proceeds as soon as the server has executed the service. The initial synchronization may