bject throughout its life protects the consistency of the database and helps modeling similar real world entities. In the relational systems, this identification number was inevitably user provided. The database is not only used for storing data but also pieces of code (methods) that run on the data. Consequently, a whole application can be stored and executed with the help of the OODBMS that also supports its maintenance. The inheritance concept makes code easily reusable. The expensive join operations of the relational systems have been substituted by the composite object notion, which combined with the clustering mechanism can improve the performance of the composite object retrieval.There are many applications that have been using the relational systems very successfully now for many years and they do not need to change. However, there are a couple of other applications especially in the engineering fields that don't do much with relational systems, mainly from the modeling aspect. For these kinds of applications, the object-oriented approach seems quite appropriate in spite of the problems that still have to be solved....
