Introducing Defeasibility into OWL Ontologies

In recent years, various approaches have been developed for representingand reasoning with exceptions in OWL. The price one pays for such capabilities,in terms of practical performance, is an important factor that is yetto be quantified comprehensively. A major barrier is the lack of naturally occurringontologies with defeasible features - the ideal candidates for evaluation.Such data is unavailable due to absence of tool support for representing defeasiblefeatures. In the past, defeasible reasoning implementations have favouredautomated generation of defeasible ontologies. While this suffices as a preliminaryapproach, we posit that a method somewhere in between these two wouldyield more meaningful results. In this work, we describe a systematic approachto modify real-world OWL ontologies to include defeasible features, and we applythis to the Manchester OWL Repository to generate defeasible ontologies forevaluating our reasoner DIP (Defeasible-Inference Platform). The results of thisevaluation are provided together with some insights into where the performancebottle-necks lie for this kind of reasoning. We found that reasoning was feasibleon the whole, with surprisingly few bottle-necks in our evaluation.