Towards tractable local closed world reasoning for the semantic web
Matthias Knorr, José Júlio Alferes, Pascal Hitzler · 2007
Abstract. Recently, the logics of minimal knowledge and negation as failure MKNF [11] was used to introduce hybrid MKNF knowledge bases [13], a pow-erful formalism for combining open and closed world reasoning for the Semantic Web. We present an extension based on a new three-valued framework includ-ing an alternating fixpoint, the well-founded MKNF model. This approach, the well-founded MKNF semantics, derives its name from the very close relation to the corresponding semantics known from logic programming. We show that the well-founded MKNF model is the least model among all (three-valued) MKNF models, thus soundly approximating also the two-valued MKNF models from [13]. Furthermore, its computation yields better complexity results (up to poly-nomial) than the original semantics where models usually have to be guessed. 1