Relation pm#generalizing_type (?,type)  fuzzy category, DO NOT USE DIRECTLY
  supertype:  partial_ordering_relation  this category only serves structuration purposes: it is instance of pm#partial_ordering_relation_type which is not instance of pm#class_of_inheritable_relation_type
  instance of:  partial_ordering_relation_type
  inverse:  specializing_type
  equal:  kind_of
  subtype:  supertype (type,type)  in the FT notation, the '<' link is only used to connect to a "strict" supertype
     subtype:  sub_class_of__subclassof__super_class__superclas (class,class)  in WebKB, use the link '<'
     subtype:  subrelation (relation_type,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:  sub_property_of (binary_relation_type,binary_relation_type)  in WebKB, use the link '<'
  subtype:  kind__type___class___instance_of__instanceof (?,class)  the '^' link in the FT notation