The IOF releases its ontologies as an ontological suite which is versioned as YYYYXX. YYYY represents the year of the release while the XX represents the release number for that year.
Within The IOF ontological suite two types of ontologies exist:
Released – Indicates an ontology that is considered to be stable and mature from a development perspective. Release notes will be provided for any changes concerning released content, and any revisions will be backward compatible with the prior version to the degree possible.
Provisional – Indicates an ontology that is considered to be under development. Provisional content is subject to change and may change substantially before release. IOF users should be aware that it is not dependable but could be used for reference and as the basis for further work.