Coordinating First-Order Multiparty Interactions

A first-order multiparty interaction is an abstraction mechanism that defines communication among a set of formal process roles. Actual processes participate in a first-order interaction by enroling into roles, and execution of the interaction can proceed when all roles are filled by distinct processes. As in CSP, enrolement statements can serve as guards in alternative commands. The enrolement guard-scheduling problem then is to enable the execution of first-order interactions through the judicious scheduling of roles to processes that are currently ready to execute enrolement guards. We present a fully distributed and message-efficient algorithm for the enrolement guard-scheduling problem, the first such solution of which we are aware. We also describe several extensions of the algorithm, including: generic roles; dynamically changing environments, where processes can be created and destroyed at run time; and nested-enrolement, which allows interactions to be nested.