Ranking Services Using Fuzzy HEXPrograms

The need to reason with knowledge expressed in both Logic Programming (LP) and Description Logics (DLs) paradigms on the Semantic Web lead to several integrating formalisms, e.g., Description Logic programs (dl-programs) allow a logic program to retrieve results from and feed results to a DL knowledge base. Two functional extensions of dl-programs are HEX programs and fuzzy dl-programs. The former abstract away from DLs, allowing for general external queries, the latter deal with the uncertain, vague, and inconsistent nature of knowledge on the Web by means of fuzzy logic mechanisms. In this paper, we generalize both HEX programs and fuzzy dl-programs to fuzzy HEX programs: a LP-based paradigm, supporting both fuzziness as well as reasoning with external sources. We define basic syntax and semantics and analyze the framework semantically, e.g., by investigating the complexity. Additionally, we provide a translation from fuzzy HEX programs to HEX programs, enabling an implementation via the dlvhex reasoner. Finally, we illustrate the use of fuzzy HEX programs for ranking services by using them to model non-functional properties of services and user preferences.