DR-DEVICE: A Defeasible Logic RDF Rule Language

Defeasible reasoning is a rule-based approach for efficient reasoning with incomplete and inconsistent information. Such reasoning is, among others, useful for ontology integration, where conflicting information arises naturally; and for the modeling of business rules and policies, where rules with exceptions are often used. In this demonstration we present a prototype system for defeasible reasoning on the Web. The system is called DR-DEVICE [4] and is capable of reasoning about RDF metadata over multiple Web sources using defeasible logic [1] rules. The system is implemented on top of CLIPS production rule system and builds upon R-DEVICE [5], an earlier deductive rule system over RDF metadata that also supports derived attribute and aggregate attribute rules. Rules can be expressed either in a native CLIPS-like language, or in an extension of the OO-RuleML [9] syntax. The operational semantics of defeasible logic are implemented through compilation into the generic rule language of R-DEVICE. This demonstration includes a complete use case of a semantic web broker that reasons about apartment renting. The most important features of DR-DEVICE are the following: • Support for multiple rule types of defeasible logic, such as strict rules, defeasible rules, and defeaters. • Support for both classical (strong) negation and negation-as-failure. • Support for conflicting literals, i.e. derived objects that exclude each other. • Direct import from the Web of RDF ontologies and data as input facts to the defeasible logic program. • Direct import from the Web of defeasible logic programs in an XML compliant rule syntax (RuleML). • Direct export to the Web of the results (conclusions) of the logic program as an RDF document.