(CCS) A mathematical model (a formal language) for describing processes, mostly used in the study of parallelism. A CCS program, written in behaviour expressions syntax denotes a process behaviour. Programs can be compared using the notion of observational equivalence. ["A Calculus of Communicating Systems", LNCS 92, Springer 1980]. ["Communication and Concurrency", R. Milner, P-H 1989]. (1994-11-29)