The Tagged Signal Model - A Preliminary Version of a Denotational Framework for Comparing Models of Computation

by Edward A. Lee and Alberto Sangiovanni-Vincentelli

Memorandum UCB/ERL M96/33, EECS, University of California, Berkeley, CA, USA 94720.

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We give a denotational framework that describes concurrent processes in very general terms as sets of possible behaviors. Compositions of processes are given as intersections of their behaviors. The interaction between processes is through signals, which are collections of events. A system is determinate if given the constraints imposed by the inputs there are exactly one or exactly zero behaviors. Each event is a value-tag pair, where the tags can come from a partially ordered or totally ordered set. Timed models are where the set of tags is totally ordered. Synchronous events share the same tag, and synchronous signals contain events with the same set of tags. Synchronous systems contain synchronous signals. Strict causality (in timed systems) and continuity (in untimed systems) ensure determinacy under certain technical conditions. The framework is used to compare certain essential features of various models of computation, including Kahn process networks, dataflow, sequential processes, concurrent sequential processes with rendezvous, and discrete-event systems.
Send comments to Edward A. Lee at eal at eecs berkeley edu .