Efficient Holistic Twig Joins in Leaf-to-Root Combining with Root-to-Leaf Way

Finding all the occurrences of a twig pattern on multiple elements in an XML document is a core operation for efficient evaluation of XML queries. Holistic twig join algorithms, TwigStack and TSGeneric, have been recognized as optimal solutions when the twig pattern only involves A-D(ancestor-descendant) relationships, while iTwigJoin can be optimal for partial twig patterns that contain A-D only or P-C (parent-child) only relationships. However, existing algorithms involve unnecessary computations and CPU cost of them can be further improved, and we in this paper mainly address this problem. We first propose three effective optimization rules to avoid those unnecessary computations, and then present two algorithms incorporated with these optimization rules to effectively answer twig patterns in leaf-to-root combining with root-to-leaf way. Experimental results on various datasets indicate that our algorithms perform significantly better than existing proposals.

• Type: Conference
• Year: 2007
• Where: DASFAA
• Authors: Guoliang Li, Jianhua Feng, Yong Zhang, Lizhu Zhou
• Keywords: DASFAA 2007, Database, Twig Join Algorithms, Twig Patterns, Unnecessary Computations