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Formal analysis of hierarchical state machines: Dedicated to Zohar Manna on his 26th birthday

In hierarchical state machines, the states can be ordinary states or superstates which are state machines themselves. The notion of hierarchical state machines was popularized by the introduction of STATECHARTS, and exists in various object-oriented software development methodologies. This paper surveys results concerning the impact of hierarchy for formal specification and verification. We present a systematic study of the complexity of model checking problems in presence of hierarchy, the succinctness afforded by hierarchy from a language-theoretic perspective, and heuristics for exploiting hierarchy in model checking tools.