Abstract. There have been several timed extensions of ACP-style process algebras with successful termination. None of them, to our knowledge, are equationally conservative (ground-)extensions of ACP with successful termination. Here, we point out some design decisions which were the possible causes of this misfortune and by taking different decisions, we propose a spectrum of timed process algebras ordered by equational conservativity ordering. 1 The Untimed Past The term “process algebra” was coined by Jan Bergstra and Jan Willem Klop in [9] to denote an algebraic approach to concurrency theory. Their process algebra had uniform atomic actions ai for i ∈ I (with I some index set), sequential composition · , choice (alternative composition) + and left-merge as the basic composition operators.1 Much of the core theory of [9] remained intact in the course of more than 20 years of developments in the ACP-school (for Algebra of Communicating Processes) of process algebra. Their the...
Jos C. M. Baeten, Mohammad Reza Mousavi, Michel A.