The ODMG Object Model: Does it Make Sense?

Abstract

The ODMG Object Model is shown to have a number of problems. A major confusion is caused by the intended type of polymorphism and the way it is expressed in the Model. Dynamic type checking is required even in situations when static type checking is possible. There are situations in which there is no way that type checking can determine whether a particular construct is type correct or not. The model of persistence in the ODMG Standard is not orthogonal, which has undesirable pragmatic consequences on complex objects. The discrepancies between the ODMG Object Model and the particular language bindings of the ODMG Standard are non-trivial. This paper presents solutions to some of these problems together with the associated formal system. Without such a formal system the recommended ODMG bindings are open to a wide range of different, and sometimes confusing interpretations. The criticism expressed in the paper is intended to be helpful in developing future releases of the ODMG Standard.