Our Ontology for Classifying Papers

The Metascience Observatory uses a custom three-level hierarchy to classify scientific work: field, discipline, and subdiscipline. The system takes some inspiration from the way that universities usually organize science into schools and majors. Below you can explore our ontology alongside the first three layers of the OpenAlex ontology. As of 2026, OpenAlex classifies scientific work into 4 domains, 26 fields, 252 subfields, and 4,516 topics. Currently, the Metascience Observatory classifies papers into 4 fields, 19 disciplines, and 115 subdisciplines. We are constantly refining and updating our ontology, with this page always showing the current version. Our system is admittadly somewhat ad-hoc, and is not intended to be systematically comprehensive like OpenAlex is. A few fields where we don't expect many replication studies are currently not included (like mathematics). OpenAlex's system also contains areas of research that are largely non-scientific in our view (like history, art).