Negation in logic programming systems

Abstract

Logic Programming languages use a uniform formulation to represent data, program, queries and newline- newlineintegrity constraint. Answering a query in a such systems is more of computation than a mere newlineretrieval of information. Only positive information can be logical consequences of a program, newlinetherefore special rules are needed to deduce negative information. Logic programs lack sufficient newlineexpressiveness for many situations. Explicit representation of negative information in logic newlineprogramming has not been feasible in many applications. The techniques for knowledge newlinerepresentation in logic programming systems can not be isolated from semantics for Logic newlinePrograms. newlineTraditionally, negation is discussed in the context of databases. However, there are several ways in newlinewhich negation can be added to clauses in first order logic. In order of increasing complexity, we newlinecould allow negated atoms in the queries, the body of the clauses or the head of clauses. In order to newlineaddress these problems to some extent we extend a class of Hom clauses that include a form of newlinenegation close to CW A called Generally Hom Logic Programs (GHLP). Covering is the basis of newlineprocedural semantics of extended program clauses. With the use of classical negation we attempt newlineto encode negati ve information for a common sense reasoning system. The operational semantics of newlinethis extension depends on the SLDNFS-resolution and Intentional Negation newlineIt is clear that some recent attempts to formulate semantics for programs with negation have newlineunderlying intuitions inspired by nonmonotonic reasoning. The use of negation or dealing with newlinenegative conditions cause nonmonotonicity in the system that rules out fixed point semantics newlineapproaches. We select rule based formulations to incorporate negative information in logic newlineprogramming system. The Censored Production Rules (CPR) and Hierarchical Censored newlineProduction Rules (HCPR) are the two formulations that inculcate features of Variable Precision newlineLogic (VPL) in a logic system.