A compositional axiomatisation of safety and liveness properties for statecharts

Statecharts is a behavioral specification language proposed for specifying large real-time, event driven, reactive systems. It is a graphical language based on state-transition diagrams for finite state machines extended with many features like hierarchy, concurrency, broadcast communication and time-out. By generating external events symbolically, Statecharts can be executed, thereby turning it into a programming language for real-time concurrency (as well as enabling rapid prototyping). As such it is amenable to compositional program verification. We supply Statecharts with a compositional proof system for both safety and liveness properties which we prove to be sound and (relatively) complete. Especially, we focus on extending compositional techniques for proving safety properties to liveness, without immediately adopting temporal logic, since that formalism, elegant as it is, introduces some difficulties with a compositional treatment of sequentiality and looping.