Session types for communicating systems in event-B.

Emergent systems are inherently communication-centered. Hence, a modeling strategy for those systems must provide the right abstractions for: (1) giving a general view of the communication patterns; (2) abstracting away from the interleaving and synchronization details; and (3) proving correct the communication schema. We propose a modeling strategy that integrates multiparty sessions types (MST) and Event-B (refinement calculus). We show how a global type, specifying the choreography that the agents must follow, can be translated into an Event-B machine describing the abstract behavior of the system (1 above). A refinement of the system leads to a model of the local types, describing declaratively the behavior of the agents involved (2 above). Relying on the type discipline and Rodin's (Event-B) theorem provers, we can prove the system correct (3 above). Our method does not require to reason about the system traces, thus easing the modeling task. We have also developed a tool that automatizes the process of generating the Event-B model from the MST specification. We illustrate our framework with three compelling distributed protocols.