Querying Optimization Research Based On XML Database

The Web technology development impelled Internet and its application development. Especially, Web development rapidly is impelled by active page technique and three-layer service model that between sever and client. Simultaneity, Web developer is conscious of limitation of current HTML, Expansibility, Configuration, Data confirmation etc aren't provided with HTML, however, those are needful for Large-scale Web application. XML technology is precisely for dealing efficaciously with the above question. At present, XML already became virtual standard of data exchange in Internet and electronic commerce. Because it has characteristics which are comprised of rich expression function,serf- description, flexibility etc, XML has been widely applied in the electronic commerce, the digital library, the intelligent Internet search and so on. However, semistructured speciality of XML datas and query way base on the path expression are differ from the relational database query, so it is limited that function that the relational database system managing XML datas. Currently,abundance XML datas that is deposited in the light of file form is in Internet. These datas included ample information,so the search way that completes query to the XML data efficiently and accurately become a study hotspot.XML has characteristic that datas and its performance can be separate and formidable data expression ability. It already became the bridge which between the Internet and the database.. Its appearance causes Internet base on text to transform into Internet base on data.—a distributed database in global scope. Nevertheless, The XML is not merely medium between the Internet and the database, it can complete more matter. The XML biggest merit is its formidable data expression ability, because it not only could express datas in relational model and object model, but also could express irregular, an changeful data, it is tyical semistructured datas.Due to XML datas has self- description characteristic, type and number of data node value are very flexible, so we cann't process them by the fixed form. It is greadtly difficult to query to XML data on account of characteristic that built-in structure and the pattern information is not integrated. It is inefficient for XML database that the traditional method which based on scanning the tree structure continually, it can not fulfil the complex processing request. In fact, computation of the XML query expression is seeks mapping process for the tree pattern to the documents tree, in...