Relation pm#supertype (pm#type,pm#type)  in the FT notation, the '<' link is only used to connect to a "strict" supertype
  supertype:  pm#relation_from_type  pm#generalizing_type
  inverse:  pm#subtype
  similar_to:  lis#specialization
  subtype:  rdfs#sub_class_of__subclassof__super_class__superclas (rdfs#class,rdfs#class)  in WebKB, use the link '<'
  subtype:  sumo#subrelation (pm#relation_type,pm#relation_type)  if the common reading conventions of parameters had been respected, this type would have been named subclass_of; every tuple of the 1st argument (r1) is also a tuple of the 2nd argument (r2), i.e. if r1 holds for some arguments arg_1, arg_2, ... arg_n, then the r2 holds for the same arguments; a consequence of this is that a relation and its subrelations must have the same valence
     subtype:  rdfs#sub_property_of (pm#binary_relation_type,pm#binary_relation_type)  in WebKB, use the link '<'