Why the Atlas exists
The Ontology Atlas pulls the world's public models into one place you can actually search. It's the companion to our writing on the subject — how to build an ontology and how to find one that already exists. Reuse is the fastest path to a world-class domain model, and this is where you start.
public ontologies, registries & vocabularies, searchable in one place
domains — from biomedicine and finance to geospatial, library and government
pulled from OBO Foundry and EBI OLS, plus domain scouts that keep discovering more
What's inside
Every entry is mapped from a public source into one consistent, searchable shape — name, domain, description, license and home link. The catalog blends a few kinds of source:
How to use it
Search by anything. On the Search page, type a domain (“disease”, “units”, “finance”), an acronym (“GO”, “FIBO”), or a plain-English description of what you're modeling — search understands meaning, not just keywords. Press / to jump straight to the search box.
Filter by domain. Use the category chips to narrow to registries, upper ontologies, cross-industry vocabularies, or a specific field. Each card links straight to the ontology's home so you can go deep.
Then reuse, don't rebuild. Anchor to the best existing model, pull in the terms you need, and enhance it to fit your domain — that's the whole game.
How we grade
Every ontology in the Atlas carries a letter grade from A to F. The grade answers a single question at a glance: is this ontology in good shape today? Freshly updated, well-referenced ontologies grade high; abandoned or dead ones grade low. The grade is not about how good an ontology is; it is about how alive it is.
The grade is a weighted score across three factors:
Recency 40% weight
Days since the ontology was last updated. Fresh (<90 days) scores 100. Very stale (5+ years) scores 10. For GitHub-hosted ontologies we use the last commit date; for OBO Foundry entries we use the registry's release date; for standards bodies we use HTTP Last-Modified.
Update frequency 35% weight
How actively the ontology is being maintained. For GitHub: commits per year (>50 = 100, >20 = 85, >10 = 70, ...). For OBO Foundry: the registry's activity_status - active (90), inactive (40), orphaned (10). For everything else: a neutral 70 if the URL is live.
References 25% weight
How widely used the ontology is. For GitHub: star count on a log scale (>500 = 100, >100 = 85, >30 = 70, ...). For OBO Foundry: the number of downstream ontologies that depend on it. For standards bodies: a per-publisher baseline (W3C, ISO, WHO, NLM = 90; academic/research = 62).
The letter scale. Weighted total (0-100) maps to a letter:
| Score | Grade | Meaning |
|---|---|---|
| 95-100 | A | Actively developed, widely referenced, freshly updated. The safest bets to reuse. |
| 90-94 | A- | Near-top: strong on almost every axis. |
| 80-89 | B+ / B | Solid and healthy - well-established with recent activity. |
| 75-79 | B- | Mature and stable. Often a foundational standard where "no updates" means "settled", not "abandoned". |
| 60-74 | C+ / C | Established but quiet. Still reusable; check that the last update predates your requirements. |
| 45-59 | D | Fading. Few recent updates, low community traction. Reuse with caution. |
| <45 | F | Dead URL, orphaned OBO status, or effectively abandoned. Don't build on top of it. |
Two edge cases. First, an ontology's URL that our URL health check flagged as broken (404, DNS failure, timeout) gets an automatic F - a dead link doesn't need a nuanced score. Second, a publisher floor prevents curated standards from being unfairly punished for being stable: OBO Foundry ontologies with active status floor at C (55); curated W3C / ISO / schema.org standards floor at C+ (60). Being in this curated catalog is itself a signal.
How often does this update? The grade is recomputed each time we regenerate the catalog (typically on data-refresh runs). If you spot a grade that looks wrong for a specific entry, the underlying components are on the ontology's detail page.
Questions
- What is an ontology?
- An ontology is a formal, explicit description of the concepts in a domain, their properties, and the rules that constrain how they relate. Unlike a database schema, it captures meaning — what a thing is and how it connects — in a machine-readable form. (“Vocabulary” and “schema” mean roughly the same thing; different communities just use different words.)
- Why reuse an existing ontology instead of building your own?
- Most domains have already been modeled by communities that have refined their work for decades. Reusing an established ontology gives you thousands of hours of domain expertise for free, keeps you interoperable with the rest of your field, and lets your AI reason over a battle-tested model instead of one built under deadline.
- Where do these ontologies come from?
- The Atlas aggregates entries live from the OBO Foundry and the EMBL-EBI Ontology Lookup Service, combined with a curated set of cross-industry and clinical standards (schema.org, Dublin Core, SKOS, FIBO, GS1, SNOMED CT, ICD-11…) and ongoing discovery from domain scouts across finance, geospatial, library, government and more.