Schema-Free XQuery

This work introduces the notion of Meaningful Lowest Common Ancestor Structure (MLCAS) for finding related nodes within an XML document and adds new functionality to XQuery to enable users to take full advantage of XQuery in querying XML data precisely and efficiently without requiring (perfect) knowledge of the document structure.

Abstract

This chapter discusses a novel XML document search technique—Schema-Free XQuery that can enable users to take full advantage of XQuery in querying XML data precisely and efficiently without requiring the full knowledge of the document schema. Schema-Free XQuery is of great potential in a data integration or data evolution context where one would like a query written once to apply "universally" and "forever." A stack-based algorithm for the Meaningful Lowest Common Ancestor Structure (MLCAS) computation at the heart of schema-free query is also presented. Investigations analyzed that this algorithm is up to sixteen times faster than a basic MLCAS computation using standard operators. Schema-free queries evaluated with this stack-based algorithm incurred an overhead no more than three times the execution time of an equivalent schema-aware query. The chapter also investigates techniques for applying MLCAS to queries involving attributes and references. Finally, the more sophisticated IR techniques are appropriate in schema-free queries.