Cost based plan selection for xpath
Proceedings of the 2009 ACM SIGMOD International Conference on Management of data
Kappa-join: efficient execution of existential quantification in XML query languages
XSym'06 Proceedings of the 4th international conference on Database and XML Technologies
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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.