Automatic generation of path conditions for concurrent timed systems

This paper presents an automatic method for calculating the path condition for programs with real time constraints. We model concurrent systems using timed transition systems and translate them into extended timed automata. Then an acyclic extended timed automaton is constructed and the path condition is calculated backwards over it. This method can be used for semiautomatic verification of a unit of code in isolation, i.e., without providing the exact values of parameters with which it is called. It can also be used for test case generation for real-time systems. Such a symbolic model checking algorithm was implemented previous in the PET system [E. Gunter, D. Peled, Unit checking: Symbolic model checking for a unit of code, Verification: Theory and Practice 2003, Essays Dedicated to Zohar Manna on the Occasion of his 64th Birthday, Lecture Notes in Computer Science, vol. 2772, Springer, 548-567] for untimed systems. Our method can also be used for the automatic generation of test cases for unit testing. The current generalization of the calculation of path condition for the timed case turns out to be quite tricky, since not only the selected path contributes to the path condition, but also timing constraints of alternative choices in the code.