Synthesizing Finite State Machines for Communication Protocols

Protocols are structured interactions among communicating agents. Traditional representations of protocols specify legal sequences of actions but define neither the content of the actions nor of the intervening states. Thus traditional representations are inadequate in open settings where autonomous agents must flexibly interact, e.g., to handle exceptions and exploit opportunities. We develop an approach in which we synthesize finite state machine representations of protocols. We first model communication protocols via commitment machines. Commitment machines supply a content to the protocol states and actions in terms of the social commitments of the participants to one another. The content can be reasoned about by the agents thereby enabling flexible execution. We provide reasoning rules to capture the evolution of commitments through the agents'' actions. Because of its representation of content and its operational rules, a commitment machine effectively encodes a systematically enhanced version of a protocol, which allows the basic sequences of actions as well as other legal moves to accommodate exceptions and opportunities. We show how a finite state machine can be synthesized from a commitment machine for efficient execution. We describe technical conditions under which our synthesis procedure yields a finite state machine that is deterministic, sound, and complete.