Analysis of the Impact of Orthogonality in the Readability of the OBO Foundry Ontologies

There is an increasing use of ontologies in the biomedical domain, so ensuring their high quality is required. Reuse of content is a best practice in ontology engineering, whose non-optimal implementation may lead to lead to loss of information and, therefore, of readability of the ontology for both humans and machines. We present twelve metrics for analyzing lack of human readability in ontologies. We applied these metrics to the OBO Foundry repository, which contains an orthogonal collection of biological and biomedical ontologies, and has content reuse as a design principle. For this study, we have also generated an orthogonal view of the repository, which can be seen as a single ontology representing the merged repository. The comparison between both perspectives permitted to identify that the readability for some types of entities and annotations decrease due to how reuse is implemented.