Relational-style XML query

  • Authors:

  • Taro L. Saito;Shinichi Morishita

  • Affiliations:

  • University of Tokyo, Tokyo, Japan;University of Tokyo, Tokyo, Japan

  • Venue:
  • Proceedings of the 2008 ACM SIGMOD international conference on Management of data
  • Year:
  • 2008

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Abstract

We study the problem of querying relational data embedded in XML. Relational data can be represented by various tree structures in XML. However, current XML query methods, such as XPath and XQuery, demand explicit path expressions, and thus it is quite difficult for users to produce correct XML queries in the presence of structural variations. To solve this problem, we introduce a novel query method that automatically discovers various XML structures derived from relational data. A challenge in implementing our method is to reduce the cost of enumerating all possible tree structures that match the query. We show that the notion of functional dependencies has an important role in generating efficient query schedules that avoid irrelevant tree structures. Our proposed method, the relational-style XML query, has several advantages over traditional XML data management. These include removing the burden of designing strict tree-pattern schemas, enhancing the descriptions of relational data with XML's rich semantics, and taking advantage of schema evolution capability of XML. In addition, the independence of query statements from the underlying XML structure is advantageous for integrating XML data from several sources. We present extensive experimental results that confirm the scalability and tolerance of our query method for various sizes of XML data containing structural variations.