Algebraic Optimization of Nested XPath Expressions

The XPath language incorporates powerful primitives for formulating queries containing nested subexpressions which are existentially or universally quantified. However, even the best published approaches for evaluating XPath have unsatisfactory performance when applied to nested queries. We examine optimization techniques that unnest complex XPath queries. For this purpose, we classify XPath expressions particularly with regard to properties that are relevant for unnesting. We present algebraic equivalences that transform nested expressions into unnested expressions. In our experiments we compare the evaluation times with existing XPath evaluators and the naive evaluation.

• Type: Conference
• Year: 2006
• Where: ICDE
• Authors: Matthias Brantner, Carl-Christian Kanne, Guido Moerkotte, Sven Helmer
• Keywords: Complex Xpath Queries, Database, ICDE 2006, XPath Evaluators, XPath Expressions