Disjunctive Deductive Databases: Semantics, Updates and
Architecture
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Abstract
The basic assumption in relational and deductive databases is that
there are no gaps in our knowledge. That is, the database cannot
store data that contain null values or data that is
indefinite. In practical situations knowledge is not precise,
and there are gaps in our knowledge. These
gaps may be due to null values in the data, may arise when we
combine several databases that lead to inconsistent theories, or may
occur because information is indefinite in nature, such as in military
or medical applications.
In this paper we describe semantics for disjunctive deductive databases
that extend the
work in deductive databases, solve the view update problem, and
permit indefinite data to be represented efficiently. Hierarchic,
stratified, and normal stable models of disjunctive databases are
described. An architecture is proposed for a disjunctive deductive
database system and a class of theories for which the architecture
will be effective is discussed.