Publisher's Synopsis
The Web Ontology Language, OWL, is the latest standard in logic based ontology languages. The Description Logic foundations of OWL mean that it is possible to compute what is entailed by an OWL ontology. However, without tool support, it can be very diffcult or impossible to understand why an entailment holds. In the OWL world, justifications, which are minimal entailing subsets of ontologies, have emerged as the dominant form of explanation. This thesis investigates justification based explanation techniques. The core of the thesis is devoted to defining and analysing Laconic and Precise Justifications. These are fine-grained justifications whose axioms do not contain any superfluous parts. An extensive empirical evaluation shows that it is practical to compute Laconic Justifications and also reveals prevalence of non-laconic justifications in the wild. The results indicate that Laconic and Precise justifications are likely to be useful in practice.
