Simulations and bisimulations are known to be useful for abstracting and comparing formal
systems, and they have recently been introduced into fuzzy systems. In this study, we …

We address the problem of computing simulation relations over tree automata. In particular,
we consider downward and upward simulations on tree automata, which are, loosely …

In this paper we deal with the verification of safety properties of infinite-state systems
modeled by term rewriting systems. An over-approximation of the set of reachable terms of a …

Visibly pushdown automata have been recently introduced by Alur and Madhusudan as a
subclass of pushdown automata. This class enjoys nice properties such as closure under all …

We investigate logics on data words, ie, words where each position is labelled by some
propositions from a finite set and by some data values from an infinite domain. A basic …

We extend an algorithm by Paige and Tarjan that solves the coarsest stable refinement
problem to the domain of trees. The algorithm is used to minimize nondeterministic tree …

This article is an introduction to the theory of finite tree automata for readers who are familiar
with standard automata theory on finite words. It covers basic constructions for ranked tree …

We study the problem of computing the transitive closure of tree-automatic (binary) relations,
which are represented by tree automata. Such relations include classes of infinite systems …

We extend an algorithm by Paige and Tarjan that solves the coarsest stable refinement
problem to the domain of trees. The algorithm is used to minimize non-deterministic tree …

We present an efficient algorithm to reduce the size of nondeterministic tree automata, while
retaining their language. It is based on new transition pruning techniques, and quotienting of …