Negation and negative information in the W3C resource description framework

Abstract

The concept of negation plays a special role in non-classical logics and also in knowledge representation formalisms where negative information has to be taken into account on par with positive information. In the tradition of mathematical logic, there is a general preference to consider positive information as basic and treat negative information as derived. This has also been the approach in relational databases, in normal logic programs, and is now again the approach in the Resource Description Framework (RDF) that has recently been proposed as a general language for representing propositional information on the Web by the World Wide Web Committee (W3C). However, as we argue in this article, any practical knowledge representation formalism, especially for the Web, has to be able to deal with knowledge items involving partial predicates for which negative information is as informative as positive information, and which may have truth-value gaps and truth-value clashes. This kind of knowledge is best represented and processed with the help of the two negations of partial logic, one expressing explicit falsity and the other one expressing non-truth.