Revision of Ontologies to Accommodate Exceptions: a Typicality-based Approach

The paper presents a methodology to revise a Description Logic knowledge base when exceptions are detected. The approach exploits concepts and results from techniques developed for debugging Description Logic terminologies. Debugging an inconsistent terminology amounts to identifying a minimal subset of axioms responsible for the inconsistency (i.e., an error to be removed by a knowledge engineer). Exception handling, instead, requires to revise the axioms causing an inconsistency so that a new consistent knowledge base is obtained, encompassing the detected exception about an individual x. To this aim, we make use of a nonmonotonic extension of the Description Logic ALC based on the combination of a typicality operator and the well established nonmonotonic mechanism of rational closure, which allows one to deal with prototypical properties and defeasible inheritance.