Negation and Quantifiers in NU-Prolog

We briefly discuss the shortcomings of negation in conventional Prolog systems. The design and implementation of the negation constructs in NU-Prolog are then presented. The major difference is the presence of explicit quantifiers. However, several other innovations are used to extract the maximum flexibility from current implementation techniques. These result in improved treatment of “if”, existential quantifiers, inequality and non-logical primitives. We also discuss how the negation primitives of NU-Prolog can be added to conventional systems, and how they can improve the implementation of higher level constructs.