Hello,

Some concepts from the FOAF ontology are used to annotate the BFO 2.0 ontology - specifically, the foaf:homepage concept is used as an annotation on the Ontology node http://purl.obolibrary.org/obo/bfo.owl.

foaf:homepage is defined in BFO 2.0 as an owl:AnnotationProperty. The FOAF ontology is not imported in BFO. The defining statement is here today in BFO 2.0 (link is to the last commit affecting the 2.0 file, 2015-08-05).

Unfortunately, the most recent version of the FOAF specification defines foaf:homepage as an owl:ObjectProperty. ("Most recent" meaning the 2014 version. The FOAF page currently links to that release stored on the Internet Archive, due to apparent recovery from an event.) This causes a graph that imports both FOAF and BFO to be inconsistent with the OWL 2 DL Profile; see OWL 2 Syntax, Section 5.8.1, "Typing Constraints of OWL 2 DL", especially the last bullet under "Property typing constraints".

I found this issue using this SHACL shape on a graph incorporating BFO's and FOAF's ontology definitions.

Is it possible for this to be corrected in BFO? I'm happy to supply a correcting PR, but am unsure of the policy on accepting contributions, or what file would be appropriate to apply a patch to. (I assume a 2.1 file is under draft somewhere, to restore properties not ported from 1.x to 2.0.)

Relatedly, I'm not sure why foaf:homepage received a local type-definition, but foaf:mbox (used in a similar role in BFO as foaf:homepage) did not. I assume homepage's definition was to relieve applications of networked concept retrievals? If this Issue results in a revision being made to 2.0 or to 2.1, foaf:mbox should also be locally defined as an owl:ObjectProperty.