Categorising logical differences between OWL ontologies

The analysis of changes between OWL ontologies (in the form of a diff ) is an important service for ontology engineering. A purely syntactic analysis of changes is insufficient to distinguish between changes that have logical impact and those that do not. The current state of the art in semantic diffing ignores logically ineffectual changes and lacks any further characterisation of even significant changes. We present a diff method based on an exhaustive categorisation of effectual and ineffectual changes between ontologies. In order to verify the applicability of our approach we apply it to 88 versions of the National Cancer Institute (NCI) Thesaurus (NCIt), and demonstrate that all categories are realized throughout the corpus. Based on the outcome of the NCIt study we argue that the devised categorisation of changes is helpful for ontology engineers and their understanding of changes carried out between ontologies.