New Rewritings and Optimizations for Regular Path Queries

  • Gösta Grahne
  • Alex Thomo
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2572)

Abstract

All the languages for querying semistructured data and the web use as an integral part regular expressions. Based on practical observations, finding the paths that satisfy those regular expressions is very expensive. In this paper, we introduce the “maximal partial rewritings” (MPR’s) for regular path queries using views. The MPR’s are always exact and more useful for the optimization of the regular path queries than other rewritings from previously known methods. We develop an algorithm for computing MPR’s and prove, through a complexity theoretic analysis, that our algorithm is essentially optimal. Also, we present query answering algorithms that utilize exact partial rewritings for regular path queries and conjunctive regular path queries respectively.

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References

  1. 1.
    S. Abiteboul, P. Buneman and D. Suciu. Data on the Web: From Relations to Semistructured Data and XML. Morgan Kaufmann, 1999.Google Scholar
  2. 2.
    S. Abiteboul, V. Vianu. Regular Path Queries with Constraints. Journal of Computing and System Sciences 58(3) 1999, pp. 428–452MATHCrossRefMathSciNetGoogle Scholar
  3. 3.
    D. Calvanese, G. Giacomo, M. Lenzerini and M. Y. Vardi. Rewriting of Regular Expressions and Regular Path Queries. Proc. of PODS 1999, pp. 194–204.Google Scholar
  4. 4.
    D. Calvanese, G. Giacomo, M. Lenzerini and M. Y. Vardi. Answering Regular Path Queries Using Views. Proc. of ICDE 2000, pp. 389–398.Google Scholar
  5. 5.
    D. Calvanese, G. Giacomo, M. Lenzerini and M. Y. Vardi. View-Based Query Processing for Regular Path Queries with Inverse. Proc. of PODS 2000, pp. 58–66.Google Scholar
  6. 6.
    D. Calvanese, G. Giacomo, M. Lenzerini and M. Y. Vardi. What is View-Based Query Rewriting? Proc. of KRDB 2000, pp. 17–27.Google Scholar
  7. 7.
    D. Florescu, A. Y. Levy, D. Suciu Query Containment for Conjunctive Queries with Regular Expressions Proc. of PODS 1998, pp. 139–148.Google Scholar
  8. 8.
    R. Goldman and J. Widom. DataGuides: Enabling query Formulation and Optimization in Semistructured Databases. Proc. of VLDB 1997 pp. 436–445.Google Scholar
  9. 9.
    G. Grahne and A. O. Mendelzon. Tableau Techniques for Querying Information Sources through Global Schemas. Proc. of ICDT 1999pp. 332–347.Google Scholar
  10. 10.
    G. Grahne and A. Thomo. An Optimization Technique for Answering Regular Path Queries. Proc. of WebDB 2000.Google Scholar
  11. 11.
    G. Grahne and A. Thomo. Algebraic Rewritings for Optimizing Regular Path Queries. Proc. of ICDT 2001 pp. 301–315.Google Scholar
  12. 12.
    G. Grahne and A. Thomo. New Rewritings and Optimizations for Regular Path Queries. http://www.cs.concordia.ca/~faculty/grahne/papers/fullicdt03.ps
  13. 13.
    J. E. Hopcroft and J. D. Ullman Introduction to Automata Theory, Languages, and Computation. Addison-Wesley 1979.Google Scholar
  14. 14.
    L. Kari. On Insertion and Deletion in Formal Languages. Ph.D. Thesis, 1991, Department of Mathematics, University of Turku, Finland.Google Scholar
  15. 15.
    A. Y. Levy. Answering queries using views: a survey. Technical Report, Computer Science Dept., Washington Univ., 2000.Google Scholar
  16. 16.
    A. Y. Levy, A. O. Mendelzon, Y. Sagiv, D. Srivastava. Answering Queries Using Views. Proc. of PODS 1995, pp. 95–104.Google Scholar
  17. 17.
    A. O. Mendelzon and P. T. Wood, Finding Regular Simple Paths in Graph Databases. SIAM J. Comp. 24:6, (December 1995).Google Scholar
  18. 18.
    Y. Papakonstantinou, V. Vassalos. Query Rewriting for Semistructured Data. Proc. of SIGMOD 1999, pp. 455–466Google Scholar
  19. 19.
    S. Yu. Regular Languages. In: Handbook of Formal Languages. G. Rozenberg and A. Salomaa (Eds.). Springer Verlag 1997, pp. 41–110Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2003

Authors and Affiliations

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

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