  Explanations for description logic (DL) entailments provide important support
for the maintenance of large ontologies. The "justifications" usually employed
for this purpose in ontology editors pinpoint the parts of the ontology
responsible for a given entailment. Proofs for entailments make the
intermediate reasoning steps explicit, and thus explain how a consequence can
actually be derived. We present an interactive system for exploring description
logic proofs, called Evonne, which visualizes proofs of consequences for
ontologies written in expressive DLs. We describe the methods used for
computing those proofs, together with a feature called signature-based proof
condensation. Moreover, we evaluate the quality of generated proofs using real
ontologies.
