Divide et Impera: Metareasoning for Large Ontologies

Ontologies have the nasty habit of growing in size and expressivity until all reasoners are at a loss to treat them in reasonable time. While it is widely known that the worst case complexity for OWL 2 DL reasoning is double exponential in time, but in fact most ontologies tend to be well behaved in practice, it is less well known that any ontology, left to itself, will grow until the worst OWL constructs gang up together and stop any reasoner from providing answers fast. We present a brand new idea to tackle this issue, by using a metareasoner which leverages best of breed reasoners and modularisation techniques to prevent the worst side effects of growing ontologies and keep query answering performance to its best. In our approach, each query will be answered by using only part of the ontology, and the best reasoner for the query will be selected on the basis of the features of this ontology portion, which is built using modularisation and/or atomic decomposition. We show the performances of an implementation of this approach. Our Chainsaw metareasoner is not designed to deal with small and inexpressive ontologies, for which a regular reasoner is more than adequate. It, instead, deals with large, complex and unwieldy ontologies, for which better solutions are not (yet) available.