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Normalization of XQuery Queries for Efficient XML Query Processing  

김서영 (삼성전자 기술총괄 소프트웨어센터)
이기훈 (한국과학기술원 전산학과)
황규영 (한국과학기술원 전산학과)
Publication Information
Journal of KIISE:Computing Practices and Letters / v.10, no.5, 2004 , pp. 419-433 More about this Journal
Abstract
As XML becomes a standard for data representation, integration, and exchange on the Web, several XML query languages have been proposed. World Wide Web Consortium(W3C) has proposed XQuery as a standard for the XML query language. Like SQL, XQuery allows nested queries. Thus, normalization rules have been proposed to transform nested XQuery queries to semantically equivalent ones that could be executed more efficiently. However, previous normalization rules are applicable only to restricted forms of nested XQuery queries. Specifically, they can not handle FLWR expressions having nested expressions in the where clause. In this paper, we propose normalization rules for XQuery queries by extending those for SQL queries. Our proposed rules can handle FLWR expressions haying nested expressions in every clause. The major contributions of this paper are as follows. First, we classily nesting types of XQuery queries according to the existence of correlation and aggregation. We then propose normalization rules for each nesting type. Second, we propose detailed algorithms that apply the normalization rules to nested XQuery queries.
Keywords
XQuery; Normalization; XML Query Processing;
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