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Publications of the Ptolemy Group

Hierarchical Finite State Machines with Multiple Concurrency Models

Alain Girault, Bilung Lee, and Edward A. Lee

October 19, 1998. Revised from Technical Memorandum UCB/ERL M97/57, August 17, 1997.
Electronics Research Laboratory, Berkeley, CA 94720

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This paper studies the semantics of hierarchical finite-state machines that are composed using various concurrency models, particularly dataflow, discrete-events, and synchronous/reactive modeling. It is argued that all three combinations are useful, and that the concurrency model can be selected independently of the decision to use hierarchical FSMs. In contrast, most formalisms that combine FSMs with concurrency models, such as Statecharts (and its variants) and hybrid systems, tightly integrate the FSM semantics with the concurrency semantics. An implementation that supports three combinations is described.
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