NoHR: An Overview Reasoning with Ontologies and Nonmonotonic Rules

Description logic ontologies, such as ontologies written in OWL, and non-monotonic rules, as known in Logic Programming, are two major approaches in Knowledge Representation and Reasoning. Even though their integration is challenging due to their inherent differences, the need to combine their distinctive features stems from real world applications. In this paper, we give an overview of NoHR, a reasoner designed to answer queries over theories composed of an OWL ontology in a Description logic and a set of non-monotonic rules. NoHR has been developed as a plug-in for the widely used ontology editor Protege, building on a combination of reasoners dedicated to OWL and rules, but it is also available as a library, allowing for its integration within other environments and applications. It comes with support for all polynomial OWL profiles and the integration of their constructors as well as for standard built-in Prolog predicates, and allows the direct consultation of databases during query evaluation and the usage of sophisticated mechanisms, such as tabling already computed results, all of which enhances the applicability and the efficiency of query answering.