Testing equivalences for event structures

A flexible abstraction mechanism for models of concurrency, which allows to consider as equivalent systems which "look the same" when observed from the outside, is proposed. It is obtained by factoring event structures, a basic model of parallelism, by means three observational equivalences defined in the testing equivalence style. By using three classes of atomic observations, namely sequences of actions, sequences of multisets of actions and partial orderings of actions, different information about the causal and temporal structure of processes is captured. As a result three different c1asses of event structures which allow to capture three different semantic models for concurrent systems are obtained. This three classes of event structures can be used as the basis for defining interleaving, multisets or partial ordering semantics of concurrent systems. The common framework which has been use allows to understand the relationships amongst these three common approach to the semantics of concurrent communicating systems.