An Effective Semantic Cache for Exploiting XPath Query/View Answerability

Maintaining a semantic cache of materialized XPath views inside or outside the database is a novel, feasible and efficient approach to facilitating XML query processing. However, most of the existing approaches incur the following disadvantages: 1) they cannot discover enough potential cached views sufficiently to effectively answer subsequent queries; or 2) they are inefficient for view selection due to the complexity of XPath expressions. In this paper, we propose SCEND, an effective Semantic Cache based on dEcompositioN and Divisibility, to exploit the XPath query/view answerability. The contributions of this paper include: 1) a novel technique of decomposing complex XPath queries into some much simpler ones, which can facilitate discovering more potential views to answer a new query than the existing methods and thus can adequately exploit the query/view answerability; 2) an efficient view-section method by checking the divisibility between two positive numbers assigned to queries and views; 3) a cache-replacement approach to further enhancing the query/view answerability; 4) an extensive experimental study which demonstrates that our approach achieves higher performance and outperforms the existing state-of-the-art alternative methods significantly.