Views in OODBMS are a concept which is heavily opted for by key database people but rather seldomly implemented in commercial systems. They are an important mechanism to modularize information systems and to gain logical data independence. This paper presents a concept for updateable views in OODBMS which separates application programs from the conceptual schema by introducing a layer of external schemas. Our approach supports all the traditional purposes of views and is based on a clear distinction of and division between external and conceptual schemas. The external schemas can be used much in the same way by applications as a conceptual schema could be used. In particular, special attention is given to dynamic binding and invariant (steady) method resolution with respect to static types. This method steadiness ensures that the most special method is found even across schema boundaries. We discuss some aspects of views in OODBMS, concentrating on coupling characteristics, change transparency and security, and we make brief architectural considerations for the implementation of a view system.

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