Basic Formal Ontology
Top-level ontology for scientific data integration. ISO/IEC 21838-2 standard. Foundation for 500+ OBO Foundry ontologies.
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Where this one tends to earn its keep.
Foundation for 500+ OBO Foundry biomedical ontologies
US Department of Defense data integration standard
Base layer for Industrial Ontology Foundry
Align heterogeneous scientific databases across domains
CC-BY-4.0Basic Formal Ontology (BFO), licensed under CC BY 4.0. Source: https://basic-formal-ontology.org/
Verified against the licence text on 2026-08-07.
Others worth a look in Foundational.