Defaults in Open World Relational Databases

Navin Viswanath, Rajshekhar Sunderraman.

The Open World Assumption (OWA) has been found to be necessary in a number of applications. In this paper, we study the issue of incompleteness in an open world database. We define an extension of the relational model which has two forms of negation - the explicit negation, in which certain atoms are known to be false, and a default negation which is a form of non-monotonic negation for unknown atoms in the relation. We define operators for this extended relational model. We show that this model is a generalization of the relational model in the sense that we obtain some intuitive answers in the negative component in addition to the answers obtained in the relational model.

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