Visualizing ontologies with AberOWL

Ontologies are formal theories that specify the kinds of entities and relations found in a domain. To quickly gain access to the content and structure of ontologies, ontology visualization techniques are commonly used. Visualization of ontologies often uses representations of hierarchical structures that are extracted from ontologies, most notably representations of the taxonomic relationships between classes. These graph-based representations can also be used to visualize structural changes in ontologies. We have developed a novel visualization environment for ontologies in which automated reasoning is used to generate a graph-based representation of an ontology's deductive closure, and subclass relations as well as description logic axioms that are entailed to hold between two classes are represented visually. The visualization environment can also be used to show differences between the entailed axioms of different ontology versions. The source code of the visualization environment is freely available, and we added our visualization environment to AberOWL (http://aber-owl.net), an ontology repository that contains over 400 ontologies, all of which can now be visually explored using our system.