Bisimulation and Divergence

Abstract Behavioural preorders based on the idea of bisimulation but refining the notion of bisimulation equivalence and providing explicit treatments of the phenomenon of divergence in communicating systems are investigated. Particular study is made of these preorders in the context of Milner's Calculus of Communicating Systems. The precongruence relations generated by the preorders are characterized and axiomatized on the classes of finite closed terms and sequential terms. A verification technique based on the theory of the preorders is introduced and illustrated.