Distributed automata in an assumption-commitment framework

We propose a class of finite state systems of synchronizing distributed processes, where processes make assumptions at local states about the state of other processes in the system. This constrains the global states of the system to those where assumptions made by a process about another are compatible with the commitments offered by the other at that state. We model examples like reliable bit transmission and sequence transmission protocols in this framework and discuss how assumption-commitment structure facilitates compositional design of such protocols. We prove a decomposition theorem which states that every protocol specified globally as a finite state system can be decomposed into such an assumption compatible system. We also present a syntactic characterization of this class using top level parallel composition. The main results here were first reported in an earlier paper (Mohalik & Ramanujam 1998). We thank the anonymous reviewers for detailed comments that helped to improve the presentation