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An Optimization Technique for Answering Regular Path Queries

  • Gösta Grahne
  • Alex Thomo
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1997)

Abstract

Rewriting queries using views is a powerful technique that has applications in data integration, data warehousing and query optimization. Query rewriting in relational databases is by now rather well investigated. However, in the framework of semistructured data the problem of rewriting has received much less attention. In this paper we identify some difficulties with currently known methods for using rewritings in semistructured databases. We study the problem in a realistic setting, proposed in information integration systems such as the Information Manifold, in which the data sources are modelled as sound views over a global schema. We give a new rewriting, which we call the possibility rewriting, that can be used in pruning the search space when answering queries using views. The possibility rewriting can be computed in time polynomial in the size of the original query and the view definitions. Finally, we show by means of a realistic example that our method can reduce the search space by an order of magnitude.

Keywords

Regular Expression Regular Language Query Optimization Conjunctive Query Graph Database 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2001

Authors and Affiliations

  • Gösta Grahne
    • 1
  • Alex Thomo
    • 1
  1. 1.Concordia UniversityConcordia

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