Zenoness for Timed Pushdown Automata

Timed pushdown automata are pushdown automata extended with a finite set of real-valued clocks. Additionaly, each symbol in the stack is equipped with a value representing its age. The enabledness of a transition may depend on the values of the clocks and the age of the topmost symbol. Therefore, dense-timed pushdown automata subsume both pushdown automata and timed automata. We have previously shown that the reachability problem for this model is decidable. In this paper, we study the zenoness problem and show that it is EXPTIME-complete.Comment: In Proceedings INFINITY 2013, arXiv:1402.661

Master index

Pla general, del mural ceràmic que decora una de les parets del vestíbul de la Facultat de Química de la UB. El mural representa diversos símbols relacionats amb la química

Past Pushdown Timed Automata and Safety Verification

We consider past pushdown timed automata that are discrete pushdown timed automata with past formulas as enabling conditions. Using past formulas allows a past pushdown timed automaton to access the past values of the finite state variables in the automaton. We prove that the reachability (i.e., the set of reachable configurations from an initial configuration) of a past pushdown timed automaton can be accepted by a nondeterministic reversal-bounded counter machine augmented with a pushdown stack (i.e., a reversalbounded NPCM). By using the known fact that the emptiness problem for reversal-bounded NPCMs is decidable, we show that model-checking past pushdown timed automata against Presburger safety properties on discrete clocks and stack word counts is decidable. We also investigate the reachability problem for a class of transition systems under some fairness constraints in the form of generalized past formulas. Finally, we present an example AS-TRAL specification to demonstrate the usefulness of the results