Study On XML-Based General Data Access Model

.NET heterogeneous data accessing strategy has rendered a very good solution to the integration of several distributed, heterogeneous and autonomous databases.But with the rapid development of the networks,heterogeneous data accessing has to manage not only the structured data in traditional databases but file system as well.The integration of semistructured data and nostructured data in file system is a new challenge to heterogeneous data accessing strategies.How to obtain and integrate database system and file system data in .NET and forward an integrated view to the users has become a very important issue in this research area.After analyzing the research achievements in structured data, semistructured data, nostructured data and XML,we put forward an approach to integrate data from heterogeneous data sources. Aimed at the characteristics of XML, this approach uses XML as medial data model for the integration of heterogeneous data sources and how to change structured data,semistructured data and nostructured data to XML's model,solving the semantic and functional differences between them through local agents.There is also a need to extend query optimization architecture in the integration of heterogeneous data sources because of the integration of file system.Because of the big difference based on the query ability of each data sources,and all kings of data sources can turn to XML's model,we study the query optimization of XML,put forward an approach to realize the query optimization based on index,and manage the query rewriting after query.We designed and implemented a XML-based general data accessing model with .NET on above methods. The integration including semistructured data and nostructured data is introduced,which can extract data from HTML Web pages and generate a local schema,therefore provides transparent interoperability among file system data sources and existing database management systems such as Oracle8 and Sybase.