Efficient evaluation of XML twig queries with keyword constraints

Abstract

Efficient query processing has been a critical issue for XML repositories, and recently researchers have advocated the style of full‐text search against XML documents as well. In this paper, we consider the XML query which can be represented as a query tree with twig patterns, and might consist of keyword constraints. In the proposed approach, the correspondence of each element‐keyword pair and the associated score is pre‐computed to reduce the computation loading at run time. During query processing, we will first quickly retrieve data for each path fragment represented in the query tree, which consists of only parent‐child relationships. We then construct the glued paths and match them to formulate the twig pattern. This approach focuses on where the data need to be “glued” and thus is very efficient. We demonstrate, via an extensive experimental study, that the proposed technique has great advantages over the existing approaches.