Definition of derived classes in OODBs

According to the ANSI/SPARC architecture, external schemas are derived from the database conceptual schema. In object-oriented databases (OODBs), an external schema map include classes defined in the conceptual schema just as it may also contain derived classes which are directly or indirectly defined on the basis of conceptual schema classes. In the definition of derived classes in OODBs three main issues have to be resolved, namely: the integration of derived classes with other classes in an object schema; the definition of classes with new objects; and the transmission of modifications between the objects in derived classes and those of the classes from which they are defined. A solution to the first issue was proposed by Samos (1998). In this paper, the two remaining issues are further studied and new conceptual level solutions are put forward. Our proposals are informally illustrated through some examples.

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