Relation dl#immediate_relation__immediaterelation (dl#entity,dl#entity)
  subtype:  dl#inherent_in  dl#q_location  dl#constituted_by  dl#part  dl#participant
  supertype:  dl#conceptual_relation (dl#entity,dl#entity)
     supertype:  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
        >part of:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type