From CML to its Process Algebra

Reppy's language CML extends Standard ML of Milner et al. with primitives for communication. It thus inherits a notion of strong polymorphic typing and may be equipped with a structural operational semantics. As a rst step we formulate an eeect system for statically expressing the communication behaviours of CML programs as these are not reeected in the types. As a second step we adapt the structural operational semantics of CML so as to incorporate behaviours. We then show how types and behaviours evolve in the course of computation: types may decrease and behaviours may lose preexes as well as decrease. As the syntax of behaviours is rather similar to that of a process algebra our main result may therefore be viewed as regarding the semantics of a process algebra as an abstraction of the semantics of an underlying programming language. This establishes a new kind of connection between \realistic" concurrent programming languages and \theoretical" process algebras.