Application And Research On The E-Government Data-exchange Engine Based On Metadata

Currently, the focus on E-Government system construction is changing from technology center to data center. Data have become the key-point of E-Government application system. In order to implement the data share between different E-Government systems, except for building some rules and regulations as well as strengthening the management, it is more important for us to provide some essential technology methods and software to integrate the current system resources for enhancing the share level and use efficiency of the system resources. For that, by constructing the E-Government data-exchange platform, a software system, we can realize the data-exchange and share of and between E-Government systems, and meet the requirements of data-exchange in all kinds of platforms, data resources and application systems.At first, this dissertation introduces several main projects in E-Government data-exchange technology. By comparing the advantages and disadvantages of these projects, the paper mentions a data-exchange Hub engine project, which is based on metadata exchange standard and uses XML as data description language. Meanwhile, the project cites the MDA to build the exchange metadata model, and uses an administrable center metadata database and a related principle database to actualize the registration and update of metadata as well as the modification of metadata principles database, and then, on the base of metadata standards, transfers the data by using the engine. In the system design, the data-exchange engine is composed of data interface layer, data processing/translating and business logic layers. The data interface layer formats the heterogeneous data firstly, then the engine, located in the data processing/translating and business logic layers, standardizes the data with metadata standards and principle database, and finally, through these processes, the engine forms the XML exchange files which fit the metadata standards.The experiment of the engine, which based on J2EE framework, uses EJB container to manage the metadata database and related operation logic, imports the DAO module between the application layer and the data layer, accesses the heterogeneous data resources by several EntityBeans embedded in SessionBean. Meanwhile, it uses the special SessionBean to access the metadata transform principle and transfer database data to XML by using the DOM classes. The experiment has proved that the engine can implement the data exchange methods, which use metadata as a core and take XML as data transfer intermediate, and that the engine can satisfy the design needs of the distribution, integration and variety of the share and data-exchange, possessed in the heterogeneous platforms and data resources.