Hierarchical Indexing Approach to Support XPath Queries

We study new hierarchical indexing approach to process XPath queries. Here, a hierarchical index consists of index entries that are pairs of queries and their (full/partial) answers (called extents). With such an index, XPath queries can be processed to extract the results if they match the queries maintained in those index entries. Existing XML path indexing approaches support either child-axis (/) only, or additional descendant-or-self-axis (//) but only in the query root. Different from them, we propose a novel indexing approach to process a large fragment of XPath queries, which may use /, //, and wildcards (_*). The key issues are how to reduce the number of index entries and how to maintain non-overlapping extents among index entries. We show how to compress such index and how to evaluate XPath queries on it. Experiments show the efficiency of our approaches.