XML_to_SQL Query Translation And Optimization Technology In Relational Module

XML is emerging as a standard format for both data representation and data exchange in the web. Various kinds of applications using the XML format have been developed, such as information integration, e-business, etc. Thus, huge data has to be transformed between relational format and XML format, i.e. the data obtained from web in XML format need to be stored as relational data in RDB, while the data in relational database need to be published as XML data for transmission and exchange in the web. So more and more research on using RDB to store XML data and publishing relational data in XML have been done. On the basis of comprehensive comparisons among existing technologies in XML storage domain as well as XML publishing domain, this thesis focuses on in-depth investigation of a challenging problem in both domains, i.e., how to convert XML queries over the XML documents into equivalent SQL queries over the tables.Having studied a great deal approaches to this problem in XML storage domain and XML publishing domain, we draw a conclusion that in XML storage domain, it is still a challenge to convert XQuery efficiently and no existing technologies to our best knowledge can solve this problem soundly. Moreover, this kind of conversion relies on relational schema generation,so each technique should build their own query processor. However, in XML publishing domain, there are many methods that can effectively translate most XQuery expression into an equivalent set of one or more SQL queries, and some of them are quite adaptive. Consequently, we propose a generic approach to this problem of XQuery processing in XML storage domain by means of using conversion methods from the XML publishing domain in the XML storage domain.We make it possible for most XML storage technique to use the algorithm of transforming XQuery in SilkRoute as its own query processor by constructing view forest which is the key data structure in SilkRoute. Moreover, SilkRoute has its own limitation. It can't deal with any XQuery expression based on the order of XML data. So in our approach, data structures and algorithms in SilkRoute are also ameliorated to be capable of transforming XQuery statements with sequence information. Finally, we give a conclusion of the advantages as well as drawbacks of our approach, which will guide our research work in the future.