Abstract

The representative instance is proposed as a representation of the data stored in a database whose relations are not the projections of a universal instance. Database schemes are characterized for which local consistency implies global consistency. (Local consistency means that each relation satisfies its own functional dependencies; global consistency means that the representative instance satisfies all the functional dependencies.) A method of efficiently computing projections of the representative instance is given, provided that local consistency implies global consistency. Throughout, it is assumed that a cover of the functional dependencies is embodied in the database scheme in the form of keys.

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