Although data stored in XML is of increasing importance, most existing data repositories are still managed by relational database systems. In light of this, recent XML database research has focused on extending relational database systems to handle XML data efficiently. While there are many issues in processing XML data efficiently, containment queries are the queries that often appear and need to be optimized. Recently, structural joins have been proposed to process containment queries efficiently. To date, structural join algorithms are mostly based on stacks and/or external B-Tree indices. Most of these prototypes have been implemented on object databases. This paper proposes an efficient structural join algorithm that can be implemented on top of existing relational databases. Experiments show that our method performs far more superior than previous work in both queries and updates.
William M. Shui, Franky Lam, Damien K. Fisher, Ray