Title: Unordered tree matching and ordered tree matching: the evaluation of tree pattern queries

Authors: Yangjun Chen, Leping Zou

Addresses: Department of Applied Computer Science, University of Winnipeg, Winnipeg, Manitoba, R3B 2E9, Canada. ' Department of Applied Computer Science, University of Winnipeg, Winnipeg, Manitoba, R3B 2E9, Canada

Abstract: In this paper, we study the twig pattern matching in XML document databases. Two algorithms A1 and A2 are discussed according to two different definitions of tree embedding. By the first definition, only the ancestor-descendant relationship is considered. By the second one, we take not only the ancestor-descendant relationship, but also the order of siblings into account. Both A1 and A2 are based on a subtree reconstruction technique, by which a tree structure is reconstructed according to a given set of data streams. More importantly, by revealing an interesting property of tree encoding, we show that the subtree reconstruction can be easily extended to a strategy (i.e., A1) for checking subtree matching according to the first definition with any kind of path join or join-like operations being completely avoided. A2 needs more time and space since it deals with a more difficult problem, but without join operations involved, either. The computational complexities of both algorithms are analysed, showing that they have a better performance than any existing strategy for this problem.

Keywords: XML documents; tree pattern queries; tree matching; twig pattern matching; tree embedding; tree encoding.

DOI: 10.1504/IJITCC.2011.042125

International Journal of Information Technology, Communications and Convergence, 2011 Vol.1 No.3, pp.254 - 279

Published online: 28 Aug 2011 *

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