Efficient evaluation of nearest common ancestor in XML twig queries using tree-unaware RDBMS

  • Authors:

  • Klarinda G. Widjanarko;Erwin Leonardi;Sourav S. Bhowmick

  • Affiliations:

  • School of Computer Engineering, Nanyang Technological University, Singapore;School of Computer Engineering, Nanyang Technological University, Singapore;School of Computer Engineering, Nanyang Technological University, Singapore

  • Venue:
  • DEXA'07 Proceedings of the 18th international conference on Database and Expert Systems Applications
  • Year:
  • 2007

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Abstract

Finding all occurrences of a twig pattern in a database is a core operation in XML query processing. Recent study showed that tree-aware relational framework significantly outperform tree-unaware approaches in evaluating structural relationships in XML twig queries. In this paper, we present an efficient strategy to evaluate a specific class of structural relationship called NCA-twiglet in a tree-unaware relational environment. Informally, NCA-twiglet is a subtree in a twig pattern where all nodes have the same nearest common ancestor (the root of NCA-twiglet). We focus on NCA-twiglets having parent-child relationships. Our scheme is build on top of our SUCXENT++ system. We show that by exploiting the encoding scheme of SUCXENT++ we can reduce useless structural comparisons in order to evaluate NCA-twiglets. Through a comprehensive experiment, we show that our approach is not only more scalable but also performs better than a representative tree-unaware approach on all benchmark queries with the highest observed gain factors being 352.