The Design And Implementation Of A Mediator For Heterogeneous Data Sources

The Project of NERMS (Networking Educational Resource Management System), which belongs to the Scientific and technological development plan in Jilin Province. The aim of the project is to organize and manage various kinds of educational resources effectively so that people can share and gain them efficiently. In order to satisfy the requirement for querying and managing those data with various data Sources in the NERMS project, we make a research on it and then have implemented this requirement. With the rapid development of information technology, enterprises have to face more and more information sources over a wide range from E-mail, electrical form, text file, plain file and XML to the information of commercial partners, suppliers and customers. The information may be relational or non-relational, and may be fully structured or semi-structured or unstructured. The traditional DBMS (Database Management) is unable to fit the requirement for managing and querying for the information with various kinds of data sources. And then it brings the advent of heterogeneous data sources Integration. Based the architecture of Mediator/Wrapper, it is implemented that the function of querying for those data with various kinds of data sources, which include Web resource, FTP resource and kinds of relational databases. The Working process of System is as follows: In the first place, the client application sends a high-level command, such as SQL, to the Mediator and then the Mediator parses the command; Since the data is not stored in the Mediator, the Mediator transfers the queries, which are the results of parsing the initial query command, to those Wrappers through the corresponding information in local catalog; And then, these Wrappers access those corresponding data sources. The results acquired by Wrappers are sent back to the Mediator; Finally,the Mediator merges the results from Wrappers into one and then returns it to the client.