Research On The Schema Based XQuery Optimization

With the extensive use of web, applications on Internet have been becoming more and more abundant. The technology of Internet is also promoted by kinds of web applications such as E-Bussiness, information exchange, etc. As a uniform standard for data presentation and interchange, XML came into being. Because of the natural advantages on supporting the semi-structured data, the applications of XML become popular. And the data amount produced with them become bigger and bigger. Now how to deal with these great amount of XML data is a difficult problem than perplex people. As a new query language, XQuery can solve the problems well.In this paper, we make a discussion on how to optimize the query based on XQuery1.0. And we have put forward a kind of scheme of optimization on the prototype Galax that realized by Bell Laboratory. We redesigned the two modules: XML Schema handling module and XQuery handling module. A scheme of query optimization based on Schema is brought forward. We try to make optimization based on path expressions before the XQuery normalization. At this stage, path shortening, redundant path conditions removing, contradictory conditions and satisfiability judging is done. In this way we can avoid making optimization base on CORE XQuery, which is proved to be complicated and poor efficiency. We also have explored tentatively on the issue that how to solve the performance bottleneck of Galax system by this means.