Hierarchical finite state machines with multiple concurrency models

This paper studies the semantics of hierarchical finite state machines (FSM´s) 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 FSM´s. In contrast, most formalisms that combine FSM´s 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