We consider tree automata with costs over semirings in the sense of (Seidl, 1994). We de ne the concept of a nitely factorizing semiring and of a monotonic semiring, both as the generalization of well-known particular semirings, and show that the costniteness of tree automata with costs over nitely factorizing and monotonic semirings is decidable. We show that, for tree automata with costs over...

Given a Rabin tree-language and natural numbers i, j, the language is said to be i, j-feasible if it is accepted by a parity automaton using priorities {i, i+1, ..., j}. The i, j-feasibility induces a hierarchy over the Rabin-tree languages called the Mostowski hierarchy. In this paper we prove that the problem of deciding if a language is i, j-feasible is reducible to the uniform universality ...

Tree automata with one memory have been introduced in 2001. They generalize both pushdown (word) automata and the tree automata with constraints of equality between brothers of Bogaert and Tison. Though it has a decidable emptiness problem, the main weakness of this model is its lack of good closure properties. We propose a generalization of the visibly pushdown automata of Alur and Madhusudan ...

We establish that regularly extended two-way nondeterministic tree automata with un-ranked alphabets have the same expressive power as regularly extended nondeterministic tree automata with unranked alphabets. We obtain this result by establishing regularly extended versions of a congruence on trees and of a congruence on, so called, views. Our motivation for the study of these tree models is t...

We consider the representational state complexity of unranked tree automata. The bottom-up computation of an unranked tree automaton may be either deterministic or nondeterministic, and further variants arise depending on whether the horizontal string languages defining the transitions are represented by a DFA or an NFA. Also, we consider for unranked tree automata the alternative syntactic def...

We consider co–Büchi tree automata along with both alternating and generalized paradigms, as a characterization of the class of languages whose complement is accepted by generalized Büchi tree automata. We first prove that for alternating generalized co–Büchi tree automata the simulation theorem does not hold and the generalized acceptance does not add to the expressive power of the model. Then...

When reading an input tree, a bottom-up tree automaton is \unaware" of where it is relative to the root. This problem is important to the eecient implementation of decision procedures for the Monadic Second-order Logic (M2L) on nite trees. In 7], it is shown how exponential state space blow-ups may occur in common situations. The analysis of the problem leads to the notion of guided tree automa...

Tree automata with one memory have been introduced in 2001. They generalize both pushdown (word) automata and the tree automata with constraints of equality between brothers of Bogaert and Tison. Though it has a decidable emptiness problem, the main weakness of this model is its lack of good closure properties. We propose a generalization of the visibly pushdown automata of Alur and Madhusudan ...

We present a novel, yet simple, technique for the speciication of context in structured documents that we call caterpillar expressions. Although we are primarily applying this technique in the speciication of context-dependent style sheets for HTML, SGML and XML documents, it can also be used for query speciica-tion for structured documents, as we shall demonstrate, and for the speciication of ...

We establish that regularly extended two-way nondeterministic tree automata with unranked alphabets have the same expressive power as regularly extended nondeterministic tree automata with unranked alphabets. We obtain this result by establishing regularly extended versions of a congruence on trees and of a congruence on, so called, views. Our motivation for the study of these tree models is th...