CCS: A Calculus of Communicating Systems

Abstract

The process calculus CCS for describing reactive systems is introduced. Its syntax is defined, as well as its operational semantics in terms of labeled transition systems. Some subcalculi are singled out that possess some specific interesting expressiveness properties. It is shown that CCS is Turing-complete by offering an encoding of Counter Machines into CCS. As a byproduct, all the behavioral equivalences of interest are undecidable over the class of CCS processes, even if they are decidable over some subcalculi.