On the nature of events: another perspective in concurrency

AbstractWe introduce yet another event-based formalism, that of event automata, which unifies various concepts to be found in the literature. A characteristic property of these automata is that every state bears information about the events which have happened, and every state change coincides with the happening of an event. With configurations being reachable states, we show that other formalisms, such as (prime or flow) event structures and geometric automata, can be embedded in our model. Various constructions on event automata, such as the partially synchronous products, specialize to those of other formalisms.We discuss various new concepts such as possible events, asymmetric conflict and quiescent states, all of which are of an intensional nature, and which more faithfully model certain phenomena of event-based protocols.Finally, we distinguish between specifications, and automata which satisfy a specification. This distinction seems to open new perspectives for the analysis of refinement and abstraction. We prove compositionality of satisfaction with regard to some synchronization operators