On Time and Action Lock Free Description of Timed Systems

Time and action locks can arise freely in timed automata specification. While both are error situations, time locks are by far the more serious fault. This is because their occurrence prevents any further evolution of the system. First we investigate techniques for avoiding the occurrence of timelocks. The central aspect of our solution is a redefinition of automata parallel composition based on the Timed Automata with Deadlines Framework of Bornot and Sifakis. Then the second result we present is a notion of parallel composition which preserves action lock freeness. In the sense that, if any component automaton is action lock free, then the composition will also be action lock free.