9,872 research outputs found
The Bottom-Up Position Tree Automaton, the Father Automaton and their Compact Versions
The conversion of a given regular tree expression into a tree automaton has
been widely studied. However, classical interpretations are based upon a
Top-Down interpretation of tree automata. In this paper, we propose new
constructions based on the Gluskov's one and on the one of Ilie and Yu one
using a Bottom-Up interpretation. One of the main goals of this technique is to
consider as a next step the links with deterministic recognizers, consideration
that cannot be performed with classical Top-Down approaches. Furthermore, we
exhibit a method to factorize transitions of tree automata and show that this
technique is particularly interesting for these constructions, by considering
natural factorizations due to the structure of regular expression.Comment: extended version of a paper accepted at CIAA 201
Bottom-up automata on data trees and vertical XPath
A data tree is a finite tree whose every node carries a label from a finite
alphabet and a datum from some infinite domain. We introduce a new model of
automata over unranked data trees with a decidable emptiness problem. It is
essentially a bottom-up alternating automaton with one register that can store
one data value and can be used to perform equality tests with the data values
occurring within the subtree of the current node. We show that it captures the
expressive power of the vertical fragment of XPath - containing the child,
descendant, parent and ancestor axes - obtaining thus a decision procedure for
its satisfiability problem
Logics for Unranked Trees: An Overview
Labeled unranked trees are used as a model of XML documents, and logical
languages for them have been studied actively over the past several years. Such
logics have different purposes: some are better suited for extracting data,
some for expressing navigational properties, and some make it easy to relate
complex properties of trees to the existence of tree automata for those
properties. Furthermore, logics differ significantly in their model-checking
properties, their automata models, and their behavior on ordered and unordered
trees. In this paper we present a survey of logics for unranked trees
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