Generalized Discrete Timed Automata: Decidable Approximations for Safety Verification

We consider generalized discrete timed automata with general linear relations over clocks and parameterized constants as clock constraints and with parameterized durations. We look at three approximation techniques (i.e., the r-reset-bounded approximation, the B-bounded approximation, and the hB; ricrossing-bounded approximation), and derive automata-theoretic characterizations of the binary reachability under these approximations. The characterizations allow us to show that the safety analysis problem is decidable for generalized discrete timed automata with unit durations and for deterministic generalized discrete timed automata with parameterized durations. An example specification written in ASTRAL is used to run a number of experiments using one of the approximation techniques.