Research And Implementation On Schema Transformation And Query Of XML In Data Integration

As for heterogeneous data integration system which takes relational schema as its uniform data schema, if it is based on middleware structure, there are usually two problems to be solved while integrating XML data:one is to transform XML into relational schema, the other is to transform SQL query into query aim at XML data. Based on the aforementioned problems, this paper wraps semi-structured XML data and realizes the following two functions.One is to transform XML Schema into relational schema, and the underlying data details are encapsulated. Schema transformation is the focus of this paper. A number of the existing schema mapping algorithms implement the transformation of data structure information, but not take all semantic constraints information into consideration, so these algorithms can only handle simple XML schema. Based on comprehensive study of research at home and abroad, this paper presents an indepth research on XML Schema, and puts forward the definitions of relations and constraints, according to which the paper designs a set of structural mapping rules and semantic mapping rules to correctly transform XML Schema into relational schema. The relations mapped from XML Schema do not only ensure the integrity of XML Schema information, but also preserve most of semantic constraints, and this paper proves those relations are all in BCNF.Two is to transform SQL query to XQuery, in order to query XML data fast and precisely and return the results in XML format.The whole process enables users to query XML data in the same way as querying relational data simply by means of schema mapping backup and no need to store XML data in relational databases, which realizes transparent operations of XML data.