Research And Implementation On XML-Based Query Reformulation In Data Integration

Along with the development of the Intemet,many applications find the needed data at different loeations are heterogeneous. It needs to effectively integrate the distributed heterogeneous data for developing applications. Based on these data a variety of applications have been developed,so integration of the data should not affect the existing system. Data Integration is aimed at achieving the effective integration of distributed heterogeneous data and providing transparently data access. The data providers hope that data easily provided, and ensuring the safety of their own data sources. Data users can transparently aecess the needed data without knowing too much detail.Owing to the advantage of the XML: extensible, structured and platform independent merits, XML has become to be the standard of data exchange on Internet quickly, which leads to a hot research topic on XML-based dataintegration today. It is an ideal solution to data integration. In the field of the data integration, re-written the global query into the subset query based on the data source model is a key step in the data integration system.The following are the points of this paper:(1) The problem of the XML-based data integration is addressed. Firstly, this paper introduces the XML and its related technology, the knowledge of the query reformulation and the data integration system. Secondly, the fundamental knowledge of the data integration is researched such as integration system theoretical framework, basic mapping scheme, querying operation of the integration system and so on.(2) In order to resolve the problem of the modle conversion in the processing the query reformulation, a conversion algorithm was taken in based on the XML. By defining the query language and mapping language, it generates the mapping rules. With replacing the global query by the mpping rules, the query generates the subquery finally.(3) The traditional way of data integration is far from the people's need of obtaining data. There are a lot of defects in dynamic adding or deleting datasources, supporting the interoperability among heterogeneous data sources, publishing the application services in accordance with the needs of usersand so on.Thus the paper proposes a kind of design and realizing program,which uses XML data transforming format, XML Schema to built public models, and Heterogeneous Data Access Integration Middleware(HDAIM). A public integrated environment under distributed environment is set up, which shields all differences in aspects of data source including the platform, system environment and intemal datastructure and so on. It provides a unified and transparent interface for users to implement the accession and publication of relative data among heterogeneous data sourees. We validate the feasibility and correctness of the query reformulation algorithms and integration system using a student information system. At the last part of the paper, further research and improve content was put forward.