Identification And Query Algorithm Of Extended XML Tree Pattern For XQuery Programs

With the rapid development of computer network technology, the Internet hasbecome an important channel for access to and dissemination of information, moreand more information is exchanged and shared through network. As a cross-platformextensible markup language, XML has been widely used and has become the de factostandard for Internet data description and exchange. To standardize the query andprocess of XML data, International World Wide Web (W3C) released the XML dataquery language standard XQuery language. How to implement XQuery languageefficiently has become a research hotspot.Different from the relational data, XML data is a kind of semi-structural data.XML data query contains a variety of structural joins, which are often interrelated andcan be represented as a tree-typed query pattern. This kind of tree-typed query patternexists in the XML query request described in XPath and XQuery language widely,called XML Tree Pattern Query (TPQ), or Twig Query. TPQ is the core operation ofXML query, as well as the hotspot of the studies about XML query. Include the queryrequirement described by XQuery language into XML TPQ as much as possiblecontributes to improve the efficiency of the implementable of XQuery program. Amore descriptive extended tree pattern GTP++is proposed, which supportmandatory/optional relationship, predicates and AND, OR, NOT logical operation. Atthe same time, an efficient XML tree pattern recognization algorithm is proposed,Based on this algorithm, various structural constraints can be collected from bothfor/let clause and return clause in nested FLWOR expressions, and merged into anextended XML tree pattern. Compared with existing works, more structuralconstraints can be put into a single XML tree pattern. This approach descreases thenumber of TPQ execution and traversal of an XML document. Besides, a tree patternquery algorithm against GTP++is proposed.