  Modern ontology debugging methods allow efficient identification and
localization of faulty axioms defined by a user while developing an ontology.
The ontology development process in this case is characterized by rather
frequent and regular calls to a reasoner resulting in an early user awareness
of modeling errors. In such a scenario an ontology usually includes only a
small number of conflict sets, i.e. sets of axioms preserving the faults. This
property allows efficient use of standard model-based diagnosis techniques
based on the application of hitting set algorithms to a number of given
conflict sets. However, in many use cases such as ontology alignment the
ontologies might include many more conflict sets than in usual ontology
development settings, thus making precomputation of conflict sets and
consequently ontology diagnosis infeasible. In this paper we suggest a
debugging approach based on a direct computation of diagnoses that omits
calculation of conflict sets. Embedded in an ontology debugger, the proposed
algorithm is able to identify diagnoses for an ontology which includes a large
number of faults and for which application of standard diagnosis methods fails.
The evaluation results show that the approach is practicable and is able to
identify a fault in adequate time.
