Partial-Order Process Algebra

To date, many different formalisms exist for describing and analyzing the behavior of concurrent systems. Petri nets and process algebras are two well-known classes of such formalisms. Petri-net theory is well suited for reasoning about concurrent systems in a partial-order framework; it handles causal relationships between actions of concurrent systems in an explicit way. Process algebras, on the other hand, often provide a total-order framework, which means that information about causalities is not always accurate. This chapter illustrates how to develop a partial-order process algebra in the style of ACP. It is shown how to extend such an algebraic theory with a causality mechanism inspired by Petri-net theory. In addition, the chapter clarifies the concepts of interleaving and non-interleaving process algebra; total-order semantics for concurrent systems are often incorrectly referred to as interleaving semantics.