Homomorphism resolving of XPath trees based on automata

  • Authors:

  • Ming Fu;Yu Zhang

  • Affiliations:

  • Department of Computer Science & Technology, University of Science & Technology of China, Hefei, China;Department of Computer Science & Technology, University of Science & Technology of China, Hefei, China and Laboratory of Computer Science, Chinese Academy of Sciences, Beijing, China

  • Venue:
  • APWeb/WAIM'07 Proceedings of the joint 9th Asia-Pacific web and 8th international conference on web-age information management conference on Advances in data and web management
  • Year:
  • 2007

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Abstract

As a query language for navigating XML trees and selecting a set of element nodes, XPath is ubiquitous in XML applications. One important issue of XPath queries is containment checking, which is known as a co-NP complete. The homomorphism relationship between two XPath trees, which is a PTIME problem, is a sufficient but not necessary condition for the containment relationship. We propose a new tree structure to depict XPath based on the level of the tree node and adopt a method of sharing the prefixes of multi-trees to construct incrementally the most effective automata, named XTHC (XPath Trees Homomorphism Checker). XTHC takes an XPath tree and produces the result of checking homomorphism relationship between an arbitrary tree in multi-trees and the input tree, thereinto the input tree is transformed into events which force the automata to run. Moreover, we consider and narrow the discrepancy between homomorphism relationship and containment relationship as possible as we can.