Research On Mapping Between Object-oriented Model And Relational Data Model

The mode of object-oriented development is widely used in the current software project development. There are two strategies in the object-oriented database application development, namely based on object-oriented database development and based on relational database development. Because object-oriented database technology is not yet mature, the strategy based on relational database is mostly used in the actual development.The "impedance mismatch" problem which exists between the relational database and the object-oriented development technology can be solved by the establishment of object persistence layer. The object persistence layer realizes the mapping between the relational database and the object-oriented development technology, so that the data in the application procedure and the data in the database are isolated. The maintenance and the probability of system are enhanced.The theory basis of ORM (Object/Relation Mapping) is studied in detail, including the basic concept of object-relation mapping, the mapping of object inheritance structure, and the mapping between object and relation of one-to-one, one-to-many, many-to-many.The system framework of object persistence technology is proposed and analyzed in this thesis, also a persistence layer (named YFLayer) is realized. The design and implementation of YFLayer are described in this thesis. The idea of memory mirror which improves and upgrades the system performance is presented. The realization of the persistence layer deeps the idea of software hierarchical structure, improves the efficiency of the system development, and enhances the portability and scalability of the system.To facilitate the use of the object persistence layer and automatically generate code, the design of the code generator for YFLayer is also described in this thesis.