Fast Evaluation of Multi-source Star Twig Queries in a Path Materialization-based XML Database

Despite a large body of work on xml twig query processing in relational environment, systematic study of xml join evaluation has received little attention in the literature. In this paper, we propose a novel and non-traditional technique for fast evaluation of multi-source star twig queries in a path materialization-based rdbms. A multi-source star twig joins different xml documents on values in their nodes and the XQuery graph takes a star-shaped structure. Such queries are prevalent in several domains such as life sciences. Rather than following the conventional approach of generating one huge complex sql query from a twig query, we translate a star query into a list of sql sub-queries that only materializes minimal information of underlying xml subtrees as intermediate results. We have implemented this scheme on top of a path materialization-based xml storage system called Sucxent++. Experiments carried out confirm that our proposed approach built on top of an off-the-shelf commercial rdbms has excellent real-world performance.