On Formal Semantics of Statecharts as Supported by STATEMATE.

We formalize the rigorous but informal description of the semantics of statecharts given by Harel and Naamad in [3] which corresponds to the semantics underlying the commercial tool STATEMATE. We closely follow [3] to increase confidence that our semantics actually corresponds to their informal description. In [3] the semantics is given by a detailed description of the so-called basic step algorithm. Based on a formalization of this basic step algorithm we associate to each statechart a transition system which defines its computations. This is the first step towards linking the language of statecharts as supported by STATEMATE with other automatic verification tools. Our formalization uses Z notation rather than “standard mathematics”. This allows to structure the definition of the formal semantics and to use tools like type-checkers.