XR-tree: indexing XML data for efficient structural joins

• Published in: 2003 19th International Conference on Data Engineering pp. 253 - 264
• Main Authors: Haifeng Jiang, Hongjun Lu, Wei Wang, Ooi, B.C.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 2003
• Subjects: Computer science; Cost function; Councils; Database languages; Indexing; Information retrieval; Query processing; Spatial databases; Web sites; XML
• ISBN: 9780780376656; 078037665X
• DOI: 10.1109/ICDE.2003.1260797

XML documents are typically queried with a combination of value search and structure search. While querying by values can leverage traditional database technologies, evaluating structural relationship, specifically parent-child or ancestor-descendant relationship, between XML element sets has imposed a great challenge on efficient XML query processing. We propose XR-tree, namely, XML region tree, which is a dynamic external memory index structure specially designed for strictly nested XML data. The unique feature of XR-tree is that, for a given element, all its ancestors (or descendants) in an element set indexed by an XR-tree can be identified with optimal worst case I/O cost. We then propose a new structural join algorithm that can evaluate the structural relationship between two XR-tree indexed element sets by effectively skipping ancestors and descendants that do not participate in the join. Our extensive performance study shows that the XR-tree based join algorithm significantly outperforms previous algorithms.