Supporting Uncertainty and Inconsistency in Semantic Web Applications

Ensuring the consistency and completeness of Semantic Web ontologies is practically impossible, because of their scale and highly dynamic nature. Many web applications, therefore, must deal with vague, incomplete and even inconsistent knowledge. Rules were shown to be very effective in processing such knowledge, and future web services are expected to depend heavily on them. RuleML, which is the earliest effort to define a normalized markup for representing and exchanging rules on the web, is currently limited to Horn rules. Significant research efforts are underway to extend RuleML with more flexible representation and reasoning capabilities. This paper presents an extension of the current rule format intended to accommodate uncertain and/or inconsistent knowledge, and shows how one truth maintenance logic can be adapted and extended to support such rules.