Formalization and verification of safety properties of Statechart specifications

There have been many analysis methods proposed for the verification of safety properties of real-time systems. Most of these methods, however, are not powerful enough for complex and safety-critical real-time systems due mainly to the lack of language primitives for specifying complex requirements (e.g., ESM) or heuristic verification procedures that do not provide verification results with certainty (e.g., Statechart and Modechart). A new approach for the verification of safety properties of real-time systems is introduced. This approach adopts Statechart to specify real-time systems behaviors. The authors redefined the step semantics of Statechart to address the problems of the synchrony hypothesis inherent to the original step semantics. A operational semantics of Statechart is defined based on the step semantics and a verification method for safety properties is developed based on the operational semantics of Statechart. This method verifies safety properties using a reachability graph derived from a Statechart diagram. They did not sacrifice the practicality or expressive power of Statechart for the simplification of analysis. Useful event and action primitives including the timeout event tm() and scheduled-action sc!() are included in the analysis. A train gate system is used as an example to illustrate the concepts in the paper