A Method And Application Of Data Logical Independence Based On Metadata

Data logical independence (DLI) is an important characteristic of the database management system (DBMS), DLI could guarantee that application systems are independent of data entities, which is significant for the development of the application system. However the existing DLI solutions are insufficient because the main DLI solution is limited which is based on mapping between external schema and logical schema. In addition, due to the deficiency of information about business logic and show info in DBMS, most this kind of information need to be realized in application program. The above two points have bad influence on efficiency of development and maintenance of application greatly.In view of the above two problems, this article use metadata as an intermediate layer between application and DBMS, and much information about business logic and show info is added in metadata. Ensure DLI by combining metadata with application development technologies. The main works of this paper include:(1) Summarizes problems in the existing DLI solutions by doing some researches in depth. By analyzing the significance of DLI for application development and maintenance, expounds the important meaning of DLI for application field.(2) Put forward a thought of intermediate layer of metadata between DBMS and application system. According to the characteristics of the data entities in DBMS and business logic and show info in application, design metadata from the data tables and fields, data views, storage procedures and data report forms respectively.(3) Put forward a kind of method of automatic acquisition metadata by using DDL triggers. The method can update metadata when some changes happen in logical structure of data entities, realize the metadata changes automatically.(4) Combining metadata with application development technologies, design and realize controls integration interfaces based on metadata.(5) Apply controls integration interfaces based on metadata to development process of a practical application project. Verify that the method is effectual in ensuring DLI and improving the application efficiency of development and maintenance.