Relation pm#relation_to_another_ontology (pm#ontology,pm#ontology)
  supertype:  pm#relation_from_an_ontology  pm#relation_between_collections
  instance of:  owl#ontology_property
  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)