Knowledge Propagation in Contextualized Knowledge Repositories: an Experimental Evaluation

As the interest in the representation of context dependent knowledge in the Semantic Web has been recognized, a number of logic based solutions have been proposed in this regard. In our recent works, in response to this need, we presented the description logic-based Contextualized Knowledge Repository (CKR) framework. CKR is not only a theoretical framework, but it has been effectively implemented over state-of-the-art tools for the management of Semantic Web data: inference inside and across contexts has been realized in the form of forward SPARQL-based rules over different RDF named graphs. In this paper we present the first evaluation results for such CKR implementation. In particular, in first experiment we study its scalability with respect to different reasoning regimes. In a second experiment we analyze the effects of knowledge propagation on the computation of inferences.Comment: ARCOE-Logic 2014 Workshop Notes, pp. 13-2

Defeasible Reasoning in SROEL: from Rational Entailment to Rational Closure

In this work we study a rational extension $SROEL^R T$ of the low complexity description logic SROEL, which underlies the OWL EL ontology language. The extension involves a typicality operator T, whose semantics is based on Lehmann and Magidor's ranked models and allows for the definition of defeasible inclusions. We consider both rational entailment and minimal entailment. We show that deciding instance checking under minimal entailment is in general $\Pi^P_2$-hard, while, under rational entailment, instance checking can be computed in polynomial time. We develop a Datalog calculus for instance checking under rational entailment and exploit it, with stratified negation, for computing the rational closure of simple KBs in polynomial time.Comment: Accepted for publication on Fundamenta Informatica

Who Owns a Cultural Treasure?

Because of the thoughtfulness of its arguments, the range and depth of its presentation of specific cases, and the fairness with which it reveals, thinks through, and allows some validity to opposing points of view, Playing Darts with a Rembrandt is a valuable contribution to understanding which parties have, and should have, rights in key objects that comprise our collective heritage. That I am not persuaded by some of the specific arguments in the book in no way reduces my admiration for what it accomplishes