A simple assertional proof system for real-time systems

A simple proof system for a real-time system model similar to that of timed I/O automata is presented. By introducing state variables indicating the last event occurrence time and event deadline time, one can express real-time properties in terms of traditional safety and progress assertions (e.g. invariant, unless, and leads-to) which are interpreted in the standard way. As a result, one can prove them using traditional proof rules (with weak fairness assumptions being replaced by finite upper bound timing assumptions). Unlike other approaches, one does not use a current time variable. The proof system is illustrated on a real-time mutual exclusion algorithm. The authors have also applied it to examples from the timed I/O automata literature