E. Kontopoulos, N. Bassiliades, G. Antoniou, “A Non-Monotonic Reasoning System for RDF Metadata”, Proc. 11th Int. Workshop on Non-Monotonic Reasoning, pp. 285-293, Lake District area, UK, 30 May - 1 June, 2006.
Non-monotonic reasoning constitutes an approach to rea-soning with incomplete or changing information and is sig-nificantly more powerful than standard reasoning, which simply deals with universal statements. Defeasible reason-ing, a member of the non-monotonic reasoning family, of-fers the extra capability of dealing with conflicting informa-tion and can represent facts, rules and priorities among rules. The main advantages of defeasible reasoning, how-ever, are not only limited to its enhanced representational capabilities, but also feature low computational complexity compared to mainstream non-monotonic reasoning. This paper presents a system for non-monotonic reasoning on the Semantic Web called VDR-Device, which is capable of rea-soning about RDF metadata over multiple Web sources us-ing defeasible logic rules. It is implemented on top of the CLIPS production rule system and features a RuleML com-patible syntax. The operational semantics of defeasible logic are implemented through compilation into a generic deduc-tive rule language. Since the RuleML syntax may appear complex for many users, we have also implemented a graphical authoring tool for defeasible logic rules that acts as a shell for the defeasible reasoning system. The tool con-strains the allowed vocabulary through analysis of the input RDF documents, so that the user does not have to type-in class and property names.
