A Two-Step Approach for Tree-structured XPath Query Reduction

XML data consists of a very flexible tree-structure which makes it difficult to support the storing and retrieving of XML data. The node numbering scheme is one of the most popular approaches to store XML in relational databases. Together with the node numbering storage scheme, structural joins can be used to efficiently process the hierarchical relationships in XML. However, in order to process a tree-structured XPath query containing several hierarchical relationships and conditional sentences on XML data, many structural joins need to be carried out, which results in a high query execution cost. This paper introduces mechanisms to reduce the XPath queries including branch nodes into a much more efficient form with less numbers of structural joins. A two step approach is proposed. The first step merges duplicate nodes in the tree-structured query and the second step divides the query into sub-queries, shortens the paths and then merges the sub-queries back together. The proposed approach can highly contribute to the efficient execution of XML queries. Experimental results show that the proposed scheme can reduce the query execution cost by up to an order of magnitude of the original execution cost. Keywords—XML, Xpath, tree-structured query, query reduction.

[1]  Ioana Manolescu,et al.  XMark: A Benchmark for XML Data Management , 2002, VLDB.

[2]  A. S. Thoke,et al.  International Journal of Electrical and Computer Engineering 3:16 2008 Fault Classification of Double Circuit Transmission Line Using Artificial Neural Network , 2022 .

[3]  Jignesh M. Patel,et al.  Structural joins: a primitive for efficient XML query pattern matching , 2002, Proceedings 18th International Conference on Data Engineering.

[4]  Divesh Srivastava,et al.  Holistic twig joins: optimal XML pattern matching , 2002, SIGMOD '02.

[5]  Jignesh M. Patel,et al.  Structural join order selection for XML query optimization , 2003, Proceedings 19th International Conference on Data Engineering (Cat. No.03CH37405).

[6]  Dan Suciu,et al.  Optimizing regular path expressions using graph schemas , 1998, Proceedings 14th International Conference on Data Engineering.

[7]  Ioana Manolescu,et al.  A Benchmark for XML Data Management , 2002 .

[8]  David J. DeWitt,et al.  On supporting containment queries in relational database management systems , 2001, SIGMOD '01.

[9]  Minsoo Lee,et al.  An Efficient Branch Query Rewriting Algorithm for XML Query Optimization , 2005, OTM Conferences.

[10]  Quanzhong Li,et al.  Indexing and Querying XML Data for Regular Path Expressions , 2001, VLDB.

[11]  Hongjun Lu,et al.  Holistic Twig Joins on Indexed XML Documents , 2003, VLDB.

[12]  Carlo Zaniolo,et al.  Efficient Structural Joins on Indexed XML Documents , 2002, VLDB.