Analysing Syntactic Regularities in Ontologies

Syntactic regularities are repetitive structures of axioms in the asserted form of an ontology. The Regularity Inspector for Ontologies (RIO) is a framework for detecting such regularities in ontologies using cluster analysis. Detection of syntactic regularities can be used to identify parts of an ontology that have a similar syntactic structure, and could therefore provide an intuition of their construction. In this paper, we introduce uniformity in regularities, meaning the degree of diversity of regularities in an ontology. Based on this notion, we present an analysis of syntactic regularities in a variety of ontologies by applying RIO. The selected ontologies are mainly biomedical ontologies; processable BioPortal ontologies and SKOS vocabularies that represent biomedical concepts, gathered from the Web. Our analysis aims to show how syntactic regularities are formulated when a different knowledge representation language (OWL, SKOS) is used. The results have shown that the selected SKOS vocabularies were more uniform in terms of their syntactic regularities; smaller homogeneous clusters were found, and with few generalisations, but of high abstraction level and cluster coverage. Compared to SKOS vocabularies, BioPortal ontologies were regular, but more complex and less uniform. The analysis of syntactic regularities and uniformity of regularities can be helpful for gaining an intuition of the ontology design and its complexity.