The Information Sharing Technology Of Heterogeneous Databases Based On XML

Historically, there exist a variety of databases which are heterogeneous in that they store different types of data, represent data differently, use different software to manage the data and run on different computer hardware. With the father development of business collaboration and government-affair electronical publishing, the information systems often requires access to data from multiple such databases. Therefore, a new system architecture is required to make the information sharing from many heterogeneous databases, in a transparent way, while preserving their autonomy.XML has emerged as the dominant standard data exchange format for Internet-based business applications, the extensibility of XML allows the creation of generic models that integrate data from different sources.This thesis begins with an extensive survey on traditional approaches of heterogeneous databases integration, discussing the XML technology at length and comparing XML with database, then introduces an architecture to support information sharing among heterogeneous databases. The architecture provides XML global views over heterogeneous relational databases by publishing relational data as XML, and allows outer users to access these views directly or query them using XML query language. The proposed architecture translates relational databases to XML complying with the defined mapping criterion. This thesis makes three main contributions. The first discusses the mapping mechanism from database schema to DTD, and defines the XML-DB mapping criterion. The second is to build the XML global views by designing three component: Translator, Transformer and Integrator, and manage views by ViewManager component. The third provides the Xpath and extended Xquery API for users to query XML global views. In addition, a middleware named lzXMLDB has been implemented by Java language, which can be easily used to construct the information sharing platform over heterogeneous databases.