Relation pm#relation_playing_a_special_role (*)  this type permits to categorize relations according to their roles ; this is a traditional but quite subjective way of categorizing relations
  subtype: {attributive_relation mereological_relation intentional_relation temporal_relation object_relation}  conceptual_relation  relation_for_an_application  domain_related_relation
  >part of:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type