Navigation-Driven Evaluation of Virtual Mediated Views

  • Bertram Ludäscher
  • Yannis Papakonstantinou
  • Pavel Velikhov
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1777)

Abstract

The MIX mediator systems incorporates a novel framework for navigation-driven evaluation of virtual mediated views. Its architecture allows the on-demand computation of views and query results as the user navigates them. The evaluation scheme minimizes superfluous source access through the use of lazy mediators that translate incoming client navigations on virtual XML views into navigations on lower level mediators or wrapped sources. The proposed demand-driven approach is inevitable for handling up-to-date mediated views of large Web sources or query results. The non-materialization of the query answer is transparent to the client application since clients can navigate the query answer using a subset of the standard DOM API for XML documents. We elaborate on query evaluation in such a framework and show how algebraic plans can be implemented as trees of lazy mediators. Finally, we present a new buffering technique that can mediate between the fine granularity of DOM navigations and the coarse granularity of real world sources. This drastically reduces communication overhead and also simplifies wrapper development. An implementation of the system is available on the Web.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    S. Abiteboul, D. Quass, J. McHugh, J. Widom, and J. L. Wiener. The Lorel Query Language for Semistructured Data. Intl. Journal on Digital Libraries, 1(1):68–88, 1997.Google Scholar
  2. 2.
    P. Buneman, R. E. Frankel, and N. Rishiyur. An Implementation Technique for Database Query Languages. ACM TODS, 7(2):164–186, June 1982.CrossRefGoogle Scholar
  3. 3.
    V. Christophides, S. Cluet, and G. Moerkotte. Evaluating Queries with Generalized Path Expressions. In ACM SIGMOD, pp. 413–422, 1996.Google Scholar
  4. 4.
    S. Cluet, C. Delobel, J. Simeon, and K. Smaga. Your Mediators Need Data Conversion! In ACM SIGMOD, pp. 177–188, 1998.Google Scholar
  5. 5.
    W. F. Cody, et.al. Querying Multimedia Data from Multiple Repositories by Content: the Garlic Project. In VLDB, pp. 17–35, 1995.Google Scholar
  6. 6.
    Document Object Model (DOM) Level 1 Specification. http://www.w3.org/TR/REC-DOM-Level-1/, 1998.
  7. 7.
  8. 8.
    H. Garcia-Molina, J. D. Ullman, and J. Widom. Database System Implementation. Prentice Hall, 1999.Google Scholar
  9. 9.
    T. Grust and M. H. Scholl. How to Comprehend Queries Functionally. Journal of Intelligent Information Systems, 12(2/3):191–218, Mar. 1999.CrossRefGoogle Scholar
  10. 10.
  11. 11.
    B. Ludäscher, Y. Papakonstantinou, and P. Velikhov. A Framework for Navigation-Driven Lazy Mediators. In ACM Workshop on the Web and Databases, Philadelphia, 1999. http://www.acm.org/sigmod/dblp/db/conf/webdb/webdb1999.html
  12. 12.
    B. Mitschang, H. Pirahesh, P. Pistor, B. G. Lindsay, and N. Südkamp. Processing Composite Objects as Abstractions over Relational Data. In ICDE, pp. 272–282, Vienna, Austria, 1993.Google Scholar
  13. 13.
    Mix (Mediation of Information using XML) Homepage. http://www.npaci.edu/DICE/MIX/ and http://www.db.ucsd.edu/Projects/MIX/, 1999.
  14. 14.
    MIXm (MIX Mediator System). http://www.db.ucsd.edu/Projects/MIX/MIXm, 1999.
  15. 15.
    Y. Papakonstantinou, S. Abiteboul, and H. Garcia-Molina. Object Fusion in Mediator Systems. In VLDB, pp. 413–424, 1996.Google Scholar
  16. 16.
    P. Velikhov, B. Ludäscher, and Y. Papakonstantinou. Navigation-Driven Query Evaluation in the MIX Mediator System. Technical report, UCSD, 1999. http://www.db.ucsd.edu/publications/mixm.ps.gz.
  17. 17.
    XML-QL: A Query Language for XML. http://www.w3.org/TR/NOTE-xml-ql, 1998.
  18. 18.
    Extensible Markup Language (XML) 1.0. http://www.w3.org/TR/REC-xml, 1998.
  19. 19.
    XML Pointer Language (XPointer). http://www.w3.org/TR/WD-xptr.

Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Bertram Ludäscher
  • Yannis Papakonstantinou
  • Pavel Velikhov

There are no affiliations available

Personalised recommendations