Relation dl#properly_subsumes_leaf__PSBL (type,type)  the 2nd type is a leaf type properly subsumed by the 1st type
  supertype:  strict_subtype (type,type)  the '>' link in the FT notation
     supertype:  subtype__subtype_or_equal (type,type)  subtype links should actually be strict subtype links or not much checking can be done
        supertype:  specializing_type (type,?)
           supertype:  relation_from_type (type,*)  type of relations from a concept/relation type, i.e. in RDFS terminology, from a class or a property
              supertype:  relation_from_collection (collection,*)
                 supertype:  relation_from/to_thing_of_common_kind (*)  this type permits to categorize relations according to their signatures and hence offers (i) a concise way to set essential exclusion relations, and (ii) a systematic and easy-to-follow categorization
                    >part of:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
                 supertype:  what_relation (*)
                    supertype:  wh-/how_relation (*)  this type permits to categorize relations according to the usual who/what/why/where/when/how questions ; this is a traditional but very subjective and ineffective way of categorizing relations 
                       >part of:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
           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
              supertype:  reflexive_relation__reflexiverelation (?,?)  this category only serves structuration purposes: it is instance of pm#reflexive_relation_type which is not instance of pm#class_of_inheritable_relation_type
                 supertype:  binary_relation_with_particular_mathematical_property (?,?)
                    supertype:  relation_with_particular_mathematical_property (*)
                       supertype:  relation_with_particular_property (*)  this rather fuzzy type permits to group categorization schemes less common than those covered by the previous sibling categories
                          >part of:  relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
              supertype:  antisymmetric_relation__antisymmetricrelation (?,?)  this category only serves structuration purposes: it is instance of pm#antisymmetric_relation_type which is not instance of pm#class_of_inheritable_relation_type
                 supertype:  binary_relation_with_particular_mathematical_property (?,?)
              supertype:  transitive_relation (?,?)  this category only serves structuration purposes: it is instance of pm#transitive_relation_type which is not instance of pm#class_of_inheritable_relation_type
                 supertype:  binary_relation_with_particular_mathematical_property (?,?)
  supertype:  subsumes_leaf__SBL (type,type)  the 2nd type is a leaf type subsumed by the 1st type
     supertype:  subtype__subtype_or_equal (type,type)  subtype links should actually be strict subtype links or not much checking can be done