Using clausal deductive databases for defining semantics in disjunctive deductive databases

• Authors: Dietmar Seipel
• Venue: Annals of Mathematics and Artificial Intelligence
• Year: 2001

This paper investigates the novel concept of iclausal deductive databases (cd-databases), which are special normal deductive databases – i.e., deductive databases which may contain default negation in rule bodies – over a typed meta-language iLcd with a fixed set of predicate symbols, namely idis, icon, and some ibuilt-in predicate symbols. The arguments of the literals in iLcd are given by disjunctive and conjunctive clauses of a basic first-order language ℒ. iDisjunctive deductive databases (dd-databases) generalize normal deductive databases by allowing for disjunctions of atoms or literals in rule heads. We present a itransformation which maps a dd-database iD into a cd-database iDcd that talks about the clauses of iD. cd-databases provide a iflexible framework for declaratively specifying the semantics of dd-databases: we can fix a standard icontrol strategy, e.g., stable model or well-founded semantics, and vary the ilogical description iDcd for specifying different semantics. The itransformed database iDcd usually consists of a part iD⊗ which naturally expresses the rules of iD, and two generic parts which are independent of iD: iDlogic specifies ilogical inference rules like resolution and subsumption, and iDcwa specifies non-monotonic inference rules like iclosed-world-assumptions. Another iprogram transformation, which uses the idea of bringing sets of clauses to the argument level is given for ihypothetical logic programs: a hypothetical logic program iD is mapped to a classical normal logic program iD⊙, such that well-known semantics and inference methods for normal logic programs can be used for hypothetical reasoning as well.