A theory of stochastic systems. Part II: Process algebra

This paper introduces (pronounce spades), a stochastic process algebra for discrete event systems, that extends traditional process algebra with timed actions whose delay is governed by general (a.o. continuous) probability distributions. The operational semantics is defined in terms of stochastic automata, a model that uses clocks¿like in timed automata¿to symbolically represent randomly timed systems, cf. the accompanying paper [P.R. D¿Argenio, J.-P. Kateon, A theory of stochastic systems. Part I: Stochastic automata. Inf. Comput. (2005), to appear]. We show that stochastic automata and are equally expressive, and prove that the operational semantics of a term up to ¿-conversion of clocks, is unique (modulo symbolic bisimulation). (Open) probabilistic and structural bisimulation are proven to be congruences for, and are equipped with an equational theory. The equational theory is shown to be complete for structural bisimulation and allows to derive an expansion law.