Achieving adaptivity for OLAP-XML federations

ABSTRACT

Motivated by the need for more flexible OLAP systems, this paper presents work on logical integration of external data in OLAP databases, carried out in cooperation between the Danish OLAP client vendor targit and Aalborg University. Flexibility is ensured by supporting XML as the external data format, since almost all data sources can be efficiently wrapped in XML. Earlier work has resulted in an extension of the targit system, allowing external XML data to be used as dimensions and measures in OLAP databases. This work has led to a number of new idea for improving the system's ability to adapt to changes in its surroundings.This paper describes the potential problems that may interrupt the operation of the integration system, in particular those caused by the often autonomous and unreliable nature of external XML data sources, and methods for handling these problems. Specifically, we describe techniques for handling changes in external XML data sources. We also describe techniques for improving the reliability of external XML sources, e.g., when these are found on the Internet, by dynamically trying to locate alternative sources during the evaluation of a query. Finally, we discuss solutions to a number of other possible problems, and show how the techniques can be integrated in the targit architecture. Experiments performed with a prototype implementation of central functionality shows the viability of the proposed solutions.

REFERENCES

• 1: Nabil Adam , Igg Adiwijaya , Terence Critchlow , Ron Musick, Detecting Data and Schema Changes in Scientific Documents, Proceedings of the IEEE Advances in Digital Libraries 2000, p.160, May 22-24, 2000
• 2: Ron Avnur , Joseph M. Hellerstein, Eddies: continuously adaptive query processing, Proceedings of the 2000 ACM SIGMOD international conference on Management of data, p.261-272, May 15-18, 2000, Dallas, Texas, United States
• 3: G. Cobéna, S. Abiteboul, and A. Marian. Detecting Changes in XML Documents. In Proc. of ICDE, 2002.
• 4: Google Inc. www.google.com. Current as of June 30th, 2003.
• 5: Amélie Marian , Serge Abiteboul , Gregory Cobena , Laurent Mignet, Change-Centric Management of Versions in an XML Warehouse, Proceedings of the 27th International Conference on Very Large Data Bases, p.581-590, September 11-14, 2001
• 6: Benjamin Nguyen , Serge Abiteboul , Grégory Cobena , Mihaí Preda, Monitoring XML data on the Web, Proceedings of the 2001 ACM SIGMOD international conference on Management of data, p.437-448, May 21-24, 2001, Santa Barbara, California, United States
• 7: D. Pedersen, J. Pedersen, and T. B. Pedersen. Integration of XML Data in the Targit OLAP System. Submitted for publication, 2003.
• 8: D. Pedersen and T. B. Pedersen. Synchronizing XPath Views. Submitted for publication, 2003.
• 9: Dennis Pedersen , Karsten Riis , Torben Bach Pedersen, XML-Extended OLAP Querying, Proceedings of the 14th International Conference on Scientific and Statistical Database Management, p.195-206, July 24-26, 2002 [doi>10.1109/SSDM.2002.1029721]
• 10: Amit P. Sheth , James A. Larson, Federated database systems for managing distributed, heterogeneous, and autonomous databases, ACM Computing Surveys (CSUR), v.22 n.3, p.183-236, Sept. 1990 [doi>10.1145/96602.96604]
• 11: Targit A. S. www.targit.com. Current as of June 30th, 2003.
• 12: Erick Thomsen , George Spofford , Dick Chase, Microsoft OLAP solutions, John Wiley & Sons, Inc., New York, NY, 1999
• 13: W3C. The Information and Content Exchange (ICE) Protocol. www.w3.org/TR/NOTE-ice.html.Current as of June 30th, 2003.
• 14: W3C. Extensible Markup Language (XML) 1.0 (Second Edition). www.w3.org/TR/REC-xml. Current as of June 30th, 2003.
• 15: W3C. XML Protocol Comparisons. www.w3.org/2000/03/29-XML-protocol-matrix. Current as of June 30th, 2003.
• 16: Lucie Xyleme, Xyleme: A Dynamic Warehouse for XML Data of the Web, Proceedings of the International Database Engineering & Applications Symposium, p.3-7, July 16-18, 2001
• 17: Yue Zhuge , Hector Garcia-Molina, Graph Structured Views and Their Incremental Maintenance, Proceedings of the Fourteenth International Conference on Data Engineering, p.116-125, February 23-27, 1998

INDEX TERMS

Primary Classification:
  H. Information Systems
  H.2 DATABASE MANAGEMENT
      H.2.4 Systems
          Subjects: Distributed databases

General Terms:
Performance, Reliability

Keywords:
OLAP, XML, adaptivity, federated databases