Distinguishing Typing and Classification in Object Data Models

The notion of type has played a double role in database systems in that it has been used both to describe values stored in the database and also concepts of the application domain. In the context of object data models, we argue for a clear separation of these two roles into typing and classification, respectively. Typing is concerned with database representation while classification is concerned with models of reality in terms of entity categories and their interdependencies. We discuss this distinction and the benefits that it affords in terms of both conceptual modelling and object data model genericity. 1 Introduction There has been much discussion on the role of "type" in the fields of Programming Languages, Data Models and Knowledge Representation (see for example [BMe84, BZ81]). The debate centres on such issues as whether "type" is an intensional or extensional notion. In the case where it is intensional, there are further differences as to whether it is definitional in that i..