This document describes Basic Formal Ontology (BFO), which is an ontology that is conformant to the requirements specified for top-level ontologies in ISO/IEC 21838‑1.


It describes BFO as a resource designed to support the interchange of information among heterogeneous information systems. The following are within the scope of this document:


—    definitions of BFO-2020 terms and relations;


—    axiomatizations of BFO-2020 in OWL 2 and CL;


—    documentation of the conformity of BFO-2020 to the requirements specified for top-level ontologies in ISO/IEC 21838‑1;


—    specification of the requirements for a domain ontology if it is to serve as a module in a suite of ontologies in which BFO serves as top-level ontology hub by providing a starting point for the introduction of the most general terms in those domain ontologies which are its nearest neighbours within the suite;


—    specification of the role played by the terms in BFO in the formulation of definitions and axioms in ontologies at lower levels that conform to BFO.


The following are outside the scope of this document:


—    specification of ontology languages, including the languages RDF, OWL, and CL standardly used in ontology development;


—    specification of methods for reasoning with ontologies;


—    specification of translators between the notations of ontologies developed in different ontology languages.