Bottom-up automata on data trees and vertical XPath

Authors Diego Figueira, Luc Segoufin

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Diego Figueira
Luc Segoufin

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Diego Figueira and Luc Segoufin. Bottom-up automata on data trees and vertical XPath. In 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011). Leibniz International Proceedings in Informatics (LIPIcs), Volume 9, pp. 93-104, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2011)


A data tree is a 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, enriched with epsilon-transitions that perform tests on the data values of the subtree. 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.
  • Decidability
  • XPath
  • Data trees
  • Bottom-up tree automata


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