Comparison and Evaluation of Ontologies for Units of Measurement

Measurement units and their relations like conversions or quantity kinds play an important role in many applications. Thus, many ontologies covering this area have been developed. Consequently, for new projects aiming at reusing one of these ontologies, the process of evaluating them has become more and more time consuming and cumbersome. We evaluated eight well known ontologies for measurement units and the relevant parts of the Wikidata corpus. We automatically collected descriptive statistics about the ontologies and scanned them for potential errors, using an extensible collection of scripts. The computational results were manually reviewed, which uncovered several issues and misconceptions in the examined ontologies. The issues were reported to the ontology authors. This caused new bugfix releases in three cases. In this paper we will present the evaluation results including statistics as well as an overview of detected issues. We thereby want to enable a well-founded decision upon the unit ontology to use. Further, we hope to prevent errors in the future by describing some pitfalls in ontology development—not limited to the domain of measurement units.