NoHR: Querying EL with Non-monotonic rules

We present NoHR, a Protege plug-in that allows the user to take an EL+ ontology, add a set of non-monotonic (logic programming) rules – suitable e.g. to express defaults and exceptions – and query the combined knowledge base. Provided the given ontology alone is consistent, the system is capable of dealing with potential inconsistencies between the ontology and the rules, and, after an initial brief pre-processing period utilizing OWL 2 EL reasoner ELK, returns answers to queries at an interactive response time by means of XSB Prolog.