Evaluating contained rewritings for XPath queries on materialized views

In this paper, we study the problem how to efficiently evaluate a set of contained rewritings on materialized views. Previous works focused on how to find a set of contained rewritings given a view and a query, but did not address how to evaluate the rewritings on materialized views. To evaluate a potential exponential number of contained rewritings, we design two algorithms, a basic algorithm and an optimized algorithm. Both algorithms are built on the observation that the exponential number of contained rewritings are actually composed by a linear number of component patterns. In the optimized algorithm, we further design four important pruning rules and several heuristic rules that can effectively reduce the number of component patterns we need to evaluate. The experiments demonstrate the efficiency of our algorithms.