Using DTD to Optimize XPath Query over XML Data Stream

How to efficiently process XPath query over XML stream is a fundamental problem in XML (extensive markup language) data stream management. DTD (document type definitions) can be of great help in improving XML query efficiency, however, most current algorithms do not use this effective resource. A method using DTD structural information is proposed to process XML data stream query. The method has the following features: Tree automata is employing to express XPath; by matching XPath tree automata and DTD tree, DTD nodes that do not match the structure of XPath query are pre-marked; a novel index method of XML data stream——DBXSI (DTD-based XML stream index) is proposed; nodes and sub-trees that do not match the query are skipped by stream index when the XPath query is running. Related algorithms are also introduced. Experimental results demonstrate that the method proposed can effectively support XPath query and outperform the former work in efficiency.