We have a RO subset that is designed specifically for use in Chado databases.

The permanent URL for this is:

• http://purl.obolibrary.org/obo/ro/subsets/ro-chado.obo

This always resolves to the latest version. Permanent URLs are also available for each release, these are of the form:

• http://purl.obolibrary.org/obo/ro/releases/YYYY-MM-DD/subsets/ro-chado.obo

This different from the main releases ro.obo and ro.owl in the following respects:

• An additional stanza is added for the is_a relation
• The ontology is guaranteed to have a default-namespace: ro header
• There are no classes ([Term]s) in the file

For more background, see #68