This registry makes a distinction between an ontology and the products (also known as editions) of that ontology.

Products can be the ontology in a different format (e.g. obo vs owl), or they can be different variants (for example, subsets or extensions). They can also be ancilliary ontologies, e.g. bridge files.

Note that from an OWL format, two editions that differ in format are equivalent ontologies (they will have the same IRI), but ontology subsets etc are considered different OWLOntologies. However, from an OBO Foundry administrative perspective, the “parent” is considered the ontology.

The different products are listed as objects under the product key, for example:

layout: ontology_detail
id: go
in_foundry_order: 1
label: GO
description: An ontology for describing the function of genes and gene products
title: Gene Ontology
 - id: go.owl
 - id: go/extensions/go-plus.owl
   title: GO-Plus
   description: The core ontology plus axioms connecting to select external ontologies
 - id: go/extensions/go-taxon-groupings.owl
   title: GO Taxon Groupings
   description: Classes added to ncbitaxon for groupings such as prokaryotes

All ontologies MUST have at least one OWL product whose name corresponds to the registered id. Thus the ontology whose IRI is (known to the obofoundry as ro), must have at least the product ro.owl.

Ontologies can OPTIONALLY produce an OBO-Format file. This is conventionally the same IRI as the owl, but with .owl changed to .obo. Note that an obo product is not listed by default. If you produce an obo product, you should register it under the products field, as in the file above.

It does not matter to us if you maintain the source for your ontology in obo or owl or some hybrid. You have the option of either publishing the alternate format yourself (using a tool like ROBOT) or you can have the OBO central build pipeline do this for you. For more information, see the FAQ entry What is the Build field?.

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