Due to limitations of RDBs(relational database), deficiencies of OODBs(object oriented database) and requirements of new applications, a new trend in database area is becoming more and more obvious that relational paradigm and OO paradigm are to be unified in the database context, and RDB and OODB are to be integrated transparently. This paper first discusses three approaches for integration of RDB and OODB, and then introduces the design of a multimedia database system TH CIMHYPER in which the authors adopt the unification approach.