Compositional Semantics of ESTEREL and Verification by Compositional Reductions

We present a compositional semantics of the Esterel synchronous reactive language, in the process algebraic style of Structured Operational Semantics. We then study its interplay with various reductional transformations on the underlying automata model, focusing on compositionality and congruence properties. These properties allow early nested reductions to take place at intermediate stages during the construction of a (reduced) model, a key point in cutting down the combinatorial explosion which plagues verification of parallel programs.