Relation pm#same_type_as (pm#type,pm#type)
  supertype:  pm#relation_from_type  owl#same_as (owl)
  equal:  dl#equal (pm)
  subtype:  owl#equivalent_class (rdfs#class,rdfs#class)  in WebKB, use the link '='
  subtype:  owl#equivalent_property (pm#binary_relation_type,pm#binary_relation_type)  in WebKB, use the link '='