Relation dl#mediated_relation (dl#entity,dl#entity)
  subtype:  dl#present_at  dl#q_present_at  dl#happens_at  dl#overlaps  dl#sibling_part  dl#proper_part  dl#generic_location  dl#depends_on  dl#host
  inverse:  dl#mediated_relation
  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