Indexing Useful Structural Patterns for XML Query Processing

  • Authors:
  • Wang Lian;Nikos Mamoulis;David Wai-lok Cheung;S. M. Yiu

  • Affiliations:
  • -;-;IEEE Computer Society;-

  • Venue:
  • IEEE Transactions on Knowledge and Data Engineering
  • Year:
  • 2005

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Abstract

Queries on semistructured data are hard to process due to the complex nature of the data and call for specialized techniques. Existing path-based indexes and query processing algorithms are not efficient for searching complex structures beyond simple paths, even when the queries are high-selective. We introduce the definition of minimal infrequent structures (MIS), which are structures that 1) exist in the data, 2) are not frequent with respect to a support threshold, and 3) all substructures of them are frequent. By indexing the occurrences of MIS, we can efficiently locate the high-selective substructures of a query, improving search performance significantly. An efficient data mining algorithm is proposed, which finds the minimal infrequent structures. Their occurrences in the XML data are then indexed by a lightweight data structure and used as a fast filter step in query evaluation. We validate the efficiency and applicability of our methods through experimentation on both synthetic and real data.