Research And Implementation Of XML Query Processing Based On XQuery And Semantic Cache

With the development of the computer, communication, network and XML technology, the account of Web information which format in XML increase quickly and the information accessing become more and more frequently at the same time. But in Internet and mobile computing environment, many disadvantages, such as narrow bandwidth, frequent disconnection and the performance problems of traditional distributed database, bottlenecked querying and accessing information from Web under C/S or distributed pattern.Considering above these, this paper proposed a query processing technology based on XQuery and semantic cache for XML data in order to reduce the network communication cost and enhance the performance of query processing. The main contents of this paper are as follows:1. Deep research on semantic characters of core XQuery, and proposed a serial of normalization rules in order to simplify the query and reduce the complexity of query processing;2. With deep researching on XQuery semantic, we process the AST that parsed by XQEngine and construct SAT and TRT which can describe the XQuery semantic exactly;3. Research and analyze the existed query matching technology. Since the FWR expression is centers on variables, we proposed four query matching conditions based on SAT homomorphism with the core of tradition Tree Homomorphism arithmetic, and design the arithmetic;4. With considering the nest levels of FWR, we design a query rewriting plan based on Tag-Relation Tree(TRT) and optimise it for the purpose of reducing the difficulty of its implementation;5. With the characters of XML data and XQuery, propose a replacement strategy that combine the path express, both vacating space and keeping the hight cache rating.Finally, we implement a semantic cache of XQuery based on above techonologies, and made the performance tests under the client/server data-shipping architecture. The result shows that the query processing technology based on XQuery and semantic cache can enhance the performance of XML query on Web.