Automatic verification of real-time communicating systems by constraint-solving

In this paper, an algebra of timed processes with real{valued clocks is presented, which serves as a formal description language for real{time communicating systems. We show that requirements such as \a process will never reach an undesired state" can be veri ed by solving a simple class of constraint systems on the clock{variables. A complete method for reachability analysis associated with the language is developed, and implemented as an automatic veri cation tool based on constraint{solving techniques. Finally as examples, we study and verify the safety{properties of Fischer's mutual exclusion protocol and a railway crossing controller.