Study Of Integration Of Heterogeneous Databases On XML

As the development of database technology, information source is heterogeneous which exists in every vocation information management system which causing a lot of single information-island. But network platform is commonly used now, integrating data in heterogeneous databases effectively to share and process data better is essential. That makes the integration of heterogeneous databases an important subject.The thesis discusses the related theory of integrating the heterogeneous database, the traditional integrating means and problems. At present the technique of heterogeneous database integrating includes database transference and transform, much database system and middleware technique. Middleware technique is the better perfect precept of solving heterogeneous database which needs a sort of mutual medium.With the features of platform independency, easy extendibility, good interactivity and data semantic description and transform ability, XML is fit for mutual medium of data source. XML has emerged as the standard of data description and exchange in web quickly that allows the creation of generic model which integrates data from different databases possibly. The thesis introduces XML technology related to the heterogeneous database integration and the support of the typical database products for XML, analyses the three layers of integrating system on XML middleware which include database layer, XML middleware layer and application layer.The key to realize integration of heterogeneous databases on XML is to establish a mapping approach between databases schema and XML schema. The two familiar mapping means at present is template mapping and model mapping. The two means has some localization. The first one only supports mapping from relational databases to XML, the second has some restrict to XML document structure because of inducting model.The thesis analyzes the present algorithms and models of data mapping on XML, on the base of the analysis presentes a mapping approach based on object-tree and the algorithm that mapping between relational schema and XML schema is realized. It analyzes the mapping of data structure, semantic constraints and data type between XML Schema and relational data structure, semantic constraints and data type between XML Schema and relational database. The object-tree mapping is effective which can retain the relational database's entity integrity, referential integrity and user-defined integrity constraint. The relational schema transfers to XML schema and XML schema transfers to relational schema, the two relational schema is uniform.