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