The Normalization Theories And Algorithms In OODB Designs

With the development of Object-Oriented technologies, OODBS (Object-Oriented Database system) has been one of the most ubiquitous and promising research and application fields in recent two decades. As RDBS (Relational Database System) can hardly adapt the requirement of non-traditional applications, such as incompetence of model representations, the low system efficiency, and the simplicity of transaction model etc., OODB just adapts the requirements of non-traditional applications, and has developed into a high-integrated data system with the combination of the OO language, semantic models, complex objects. It represents a new generation of database systems. Normalization theory for object-oriented database was first brought forward in literature by Z.Tari and so on in 1997. In contrast to conventional normalization theory for relational database, the normalization theory for object-oriented database is mainly used for database conceptual design, and independent of database logical design. In this point, it makes up for the inadequacy in logical schema, and supports the object-oriented schemata. As prospering in recently years, the theory for object-oriented database has some inadequacy and is waiting to be perfected. This paper summarizes basic concepts of OODB from different angles. Then it gives the definitions of Projection Algebra and Data Dependencies. Moreover the paper elaborates on Inferential Axioms of PD and OFD for the first time, and gives their proofs. Furthermore, it also presents the definitions and theorems of Object Normal Forms (ONF) based on the data dependencies of OODB. Different from the Normal Forms of traditional database which is actually the operational criteria, whether the database model is data non-redundancy, lossless decomposition and dependency maintenance, ONF concentrates more on the precise and completeness of semantic representation of the users'interpretations of the model which is exactly the users'requirement. In the end, we give two algorithms, Transformation Algorithm and Construction Algorithm to generate ONF in database design, and analyses its complexion.