Optimization of XML Queries by Using Semantics in XML Schemas and the Document Structure

摘要

This paper proposes an approach to optimizing structural-join and twig queries for XML queries by utilizing the semantics/constraints defined in XML Schemas and the existing facilities of relational database systems. In the first stage, semantic query transformations that use constraints in the schema are utilized to transform given XML queries to equivalent semantic queries. In the second stage, the structure of a given XML document is captured and stored in a table in a relational database, which is subsequently used during query translation and execution. Conducted experiments confirm the performance benefits of our approach in optimization of XML queries before and after applying semantic query transformations as well as capturing the XML document structure. We also report in detail on the results of a comparison between the performance of our approach with those of established native and modified-relational XML database systems.