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4.7 Synchronous Reactive (SR)

The Synchronous Reactive domain, created by Stephen Edwards and documented in his Ph.D. thesis [Edw97], is a new and very experimental domain. The Synchronous Reactive domain is a statically-scheduled simulation domain in Ptolemy designed for concurrent, control-dominated systems. To allow precise control over timing, it adopts the synchronous model of time, which is logically equivalent to assuming that computation is instantaneous

SR is similar to existing Ptolemy domains, but differs from them in important ways. Like Synchronous Dataflow (SDF), it is statically scheduled and deterministic, but it does not have buffered communication or multi-rate behavior. SR is better for control-dominated systems that need control over when things happen relative to each other; SDF is better for data-dominated systems, especially those with multi-rate behavior.

SR also resembles the Discrete Event (DE) domain. Like DE, its communication channels transmit events, but unlike DE, it is deterministic, statically scheduled, and allows zero-delay feedback loops. DE is better for modeling the behavior of systems (i.e., to better understand their behavior), whereas SR is better for specifying a system's behavior (i.e., as a way to actually build it).

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