Monitoring Blackbox Implementations of Multiparty Session Protocols

We present a framework for the distributed monitoring of networks of components that coordinate by message-passing, following multiparty session protocols specified as global types. We improve over prior works by (i) supporting components whose exact specification is unknown (“blackboxes”) and (ii) covering protocols that cannot be analyzed by existing techniques. We first give a procedure for synthesizing monitors for blackboxes from global types, and precisely define when a blackbox correctly satisfies its global type. Then, we prove that monitored blackboxes are sound (they correctly follow the protocol) and transparent (blackboxes with and without monitors are behaviorally equivalent).