Relation pm#relation_from_an_ontology (ontology,*)
  supertype:  relation_from_collection
  subtype:  relation_to_another_ontology (ontology,ontology)
     subtype:  backward_compatible_with (ontology,ontology)
     subtype:  incompatible_with (ontology,ontology)
     subtype:  prior_version__priorversion (ontology,ontology)