Switched PIOA

L. Cheung, N.A. Lynch, R. Segala and F.W. Vaandrager. Switched PIOA: Parallel Composition via Distributed Scheduling. In Theoretical Computer Science 365(1-2):83-108, 2006. DOI. An earlier version of this paper appeared in ICTAC'04.


This paper presents the framework of switched probabilistic input/output automata (or switched PIOA), augmenting the original PIOA framework with an explicit control exchange mechanism. Using this mechanism, we model a network of processes passing a single token among them, so that the location of this token determines which process is scheduled to make the next move. This token structure therefore implements a distributed scheduling scheme: scheduling decisions are always made by the (unique) active component. Distributed scheduling allows us to draw a clear line between local and global non-deterministic choices. We then require that local non-deterministic choices are resolved using strictly local information. This eliminates unrealistic schedules that arise under the more common centralized scheduling scheme. As a result, we are able to prove that our trace-style semantics is compositional.