We present a concept to introduce external models in object-oriented databases to regain the traditional three level architecture of database systems consisting of an internal, a conceptual and several external models. In contrast to other approaches our concept takes into account all traditional features of external models - such as submodeling, interfacing application programs and databases, logical data independence, canned queries, and individualized access and security management. A unique advantage of this concept is the clear separation of the type and class hierarchies of the external models from those of the conceptual model allowing better and cleaner modularization of information systems built on top of object-oriented databases.

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