Relation rdfs#label (?,pm#string)  in WebKB, with FO, use the link '_'
  subtype:  dl#name  akts#has-pretty-name (pm)  akts#has-variant-name (pm)
  equal:  daml#label
  supertype:  pm#name (?,?)
     supertype:  pm#attributive_relation__attributiverelation (*)  like pm#binary_relation, this type mostly exists to categorize what cannot be categorized elsewhere
        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