Accelerating queries by pruning XML documents

Some XML query processors operate on an internal representation of XML documents and can leverage neither the XML storage structure nor the possible access methods dedicated to this storage structure. Such query processors are often used in organizations that usually process transient XML documents received from other organizations. In this paper, we propose a different approach to accelerating query execution on XML source documents in such environments. The approach is based on the notion of query equivalence of XML documents with respect to a query. Under this equivalence, we propose two different document transformation strategies which prune parts of the documents irrelevant to the query, just before executing the query itself. The proposed transformations are implemented and evaluated using a two-level index structure: a structural directory capturing document paths and an inverted index of tag offsets.