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 speaking, analogous to forward and backward relations over word automata. We provide simple and efficient algorithms for computing these relations based on a reduction to the problem of computing simulations on labelled tran...

Equational tree automata provide a powerful tree language framework that facilitates to recognize congruence closures of tree languages. In the paper we show the emptiness problem for AC-tree automata and the intersection-emptiness problem for regular AC-tree automata, each of which was open in our previous work [20], are decidable, by a straightforward reduction to the reachability problem for...

Tree pattern matching (tpm) algorithms play an important role in practical applications such as compilers and XML document validation. Many tpm algorithms based on tree automata have appeared in the literature. For reasons of efficiency, these automata are preferably deterministic. Deterministic root-to-frontier tree automata (drftas) are less powerful than nondeterministic ones, and no root-to...

Abstra t. Tree pattern mat hing (tpm) algorithms play an important role in pra ti al appli ations su h as ompilers and XML do ument validation. Many tpm algorithms based on tree automata have appeared in the literature. For reasons of eÆ ien y, these automata are preferably deterministi . Deterministi root-to-frontier tree automata (drftas) are less powerful than nondeterministi ones, and no ro...

The domains of partial attributed tree transducers (patt's) are the tree languages recognized by tree walking automata in universal acceptance mode. Moreover, the domains of patt's having monadic output are the tree languages recognized by deter-ministic tree walking automata.

Streaming validation and querying of XML documents are often based on automata for tree-like structures. We propose a new notion of streaming tree automata in order to unify the two main approaches, which have not been linked so far: automata for nested words or equivalently visibly pushdown automata, and respectively pushdown forest automata.

The purpose of this paper is to give an alternative proof to the decidability of the emptiness problem for tree automata, as shown in Rabin [4]. The proof reduces the emptiness problem for automata on infinite trees to that for automata on finite trees, by showing that any automata definable set of infinite trees must contain a finitelygenerable tree. Section 1: Introduction The analysis of fin...

An automaton model used for validation and type checking with languages defined using R2G2 [1] is presented. First, tree-shaped data is considered to be handled by the automaton model, then the approach is extended to graph shaped data. The presented approach is based on specialized non-deterministic finite state automata. The specialisation copes with unranked tree shaped data. Graph shaped da...

We propose a realizability semantics for automata on infinite trees, based on categories of games built on usual simple games, and generalizing usual acceptance games of tree automata. Our approach can be summarized with the slogan “automata as objects, strategies as morphisms”. We show that the operations on tree automata used in the translations of MSOformulae to automata (underlying Rabin’s ...

We introduce tree stack automata as a new class of automata with storage and identify a restricted form of tree stack automata that recognises exactly the multiple context-free languages.