A Special XQuery Program Dealing with Nested Loop Structure

Extract DTD documents rapidly by using pattern extraction method and eliminate the embedded ring in DTD by redefining the duplication name in document to solve the complex situation of which the embedded ring existed in XML document and the optimization scheme based on the interval encoding index can´t solve. Map back DTD which eliminate the embedded ring to XML document, analyze XQuery query statement and preprocess query. Match the path and DTD tree which eliminates the embedded ring to realize the XQuery scheme of processing structure with embedded ring.