The Emptiness Problem for Tree Automata with at Least One Disequality Constraint is NP-hard
Pierre‐Cyrille Héam, Vincent Hugot, Olga Kouchnarenko · arXiv (Cornell University) · 2014
The model of tree automata with equality and disequality constraints was introduced in 2007 by Filiot, Talbot and Tison. In this paper we show that if there is at least one disequality constraint, the emptiness problem is NP-hard.