Answering XPath Queries over Networks by Sending Minimal Views

by Keishi Tajima, Yoshiki Fukui


When a client submits a set of XPath queries to a XML database on a network, the set of answer sets sent back by the database may include redundancy in two ways: some elements may appear in more than one answer set, and some elements in some answer sets may be subelements of other elements in other (or the same) answer sets. Even when a client submits a single query, the answer can be self-redundant because some elements may be subelements of other elements in that answer. Therefore, sending those answers as they are is not optimal with respect to communication costs. In this paper, we propose a method of minimizing communication costs in XPath processing over networks. Given a single or a set of queries, we compute a minimal-size view set that can answer all the original queries. The database sends this view set to the client, and the client produces answers from it. We show algorithms for computing such a minimal view set for given queries. This view set is optimal; it only includes elements that appear in some of the final answers, and each element appears only once.

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BibTex entry


XML, XPath, minimal view, query processing, query optimization, query translation, network, communication cost, redundancy, duplication, on-line database, digital library, proxy server
Published in Proc. of VLDB, pp.48-59, Aug. 2004, Toronto, Canada

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