A State Transformation Equivalence for Concurrent Systems: Exhibited Functionality-equivalence

Most of the equivalence notions for concurrent systems proposed in recent years are defined in terms of sequences (posets) of observable actions, and therefore they are not suitable for comparing two systems whose actions are defined at different levels of detail. In this paper a new equivalence notion for concurrent systems (more precisely for contact-free S-labelled EN systems) is introduced: namely Exhibited Functionality- (EF-) equivalence. EF-equivalence is defined in terms of observable global states transformations. Its main characteristics is that it takes into account the structure of the global states of the system in terms of the local states of its components, so that it characterizes the locality of any state trasformation performed by the system components. Each EF-equivalence class of contact-free S-observable EN systems, a subclass of S-labelled EN systems, is shown to contain one and only one simple and pure contact-free EN system.