A Hybrid Approach for General XML Query Processing

Abstract

AbstractThe state-of-the-art XML twig pattern query processing algorithms focus on matching a single twig pattern to a document. However, many practical queries are modeled by multiple twig patterns with joins to link them. The output of twig pattern matching is tuples of labels, while the joins between twig patterns are based on values. The inefficiency of integrating label-based structural joins in twig pattern matching and value-based joins to link patterns becomes an obstacle preventing those structural join algorithms in literatures from being adopted in practical XML query processors. In this paper, we propose a hybrid approach to bridge this gap. In particular, we introduce both relational tables and inverted lists to organize values and elements respectively. General XML queries involving several twig patterns are processed by the both data structures. We further analyze join order selection for a general query with both pattern matching and value-based join, which is essential for the generation of a good query plan.