A Formal Method for Hard Real-Time Programming

A graphical state-transition approach to specifying hard real time reactive systems is described. This is then refined to a. formal notation based on sentences called “Non-instantaneous State-transition Assertions” (NSAs). These have a set-theoretic semantics that can be used to justify various laws, which combine aspects of Interval Temporal Logic and Hoare Logic. The semantics of programs can also be represented by sets of NSAs, and then verification is performed by using laws to combine the NSAs from the program to obtain the specification. The derivation of the laws and the mechanization of their use is in progress, but not yet complete.