Deciding Observational Congruence of Finite-State CCS Expressions by Rewriting

We propose a term rewriting approach to verify observational congruence between guarded recursive (finite-state) CCS expressions. Starting from the complete axiomatization of observational congruence for this subset of CCS, a non-terminating rewriting relation has been defined. This rewriting relation is co-canonical over a subclass of infinite derivations, structured fair derivations, which compute all the m-normal forms. The rewriting relation is shown to be complete with respect to the axiomatization by proving that every structured fair derivation computes a term that denotes an rz-normal process graph. The existence of a finite representation for o~-normal forms allows the definition of a rewritin9 strateoy that, in a finite number of rewriting steps, decides observational congruence of guarded recursive (finite-state) CCS expressions.