A direct symbolic approach to model checking pushdown systems

This paper gives a simple and direct algorithm for computing the always regular set of reachable states of a pushdown system. It then exploits this algorithm for obtaining model checking algorithms for linear-time temporal logic as well as for the logic CTL . For the latter, a new technical tool is introduced: pushdown automata with transitions conditioned on regular predicates on the stack content. Finally, this technical tool is also used to establish that CTL model checking remains decidable when the formulas are allowed to include regular predicates on the stack content.