Implementation of XPath axes in the multi-dimensional approach to indexing XML data

Abstract

XML (Extensible Mark-up Language) has been recently understood as a new approach to data modelling. An implementation of a system enabling us to store and query XML documents efficiently requires the development of new techniques which make it possible to index an XML document in a way that provides an efficient evaluation of a user query. Most XML query languages are based on the language XPath and use a form of path expressions for composing more general queries. XPath defines a family of 13 axes, i.e. relationship types in which an actual element can be associated to other elements in the XML tree. Previously published multi-dimensional approaches to indexing XML data use paged and balanced multi-dimensional data structures like UB-trees and R*-trees. In this paper we revise the approaches and introduce a novel approach to the implementation of an XPath subset.