Deciding emptiness for stack automata on infinite trees

Abstract

We show that the emptiness problem for Büchi stack automata on infinite trees is decidable in elementary time. We first establish the decidability of the emptiness problem for pushdown automata on infinite trees. This is done using a pumping-like argument applied to computation trees. We then show how to reduce the emptiness problem for stack automata to the emptiness problem for pushdown automata. Elsewhere, we have used the result to establish the decidability of several versions of nonregular dynamic logic. © 1994 Academic Press, Inc.