Coupling Fragments of XPath with XML Indexing and Query Decomposition

Abstract

Recent studies have proposed structural summary techniques for pathquery evaluation on semi-structured data sources. One major line of this research has been the introduction of the DataGuide, 1-index, 2-index, and A(k) indices, and subsequent investigations and generalizations. Another recent study has considered structural characterizations of fragments of XPath, the standard path navigation language for XML documents. In this paper we provide a methodology on XPath query processing that couples these two areas of research on structural indices and query languages. To illustrate this methodology, we apply it to couple an upward-only XPath fragment with the A(k) and P(k) structural indices.With an eye towards applying this result to XPath query processing, we (1) show how upward-only XPath expressions can be evaluated directly on the corresponding indices and (2) leverage these results to develop generic techniques for making effective use of A(k) and P(k) indices for more general, frequently occurring XPath expressions.