Function kif#nth (sumo#list,sumo#positive_integer -> ?)
  supertype:  pm#member (pm#collection,*)
     supertype:  pm#relation_from_collection (pm#collection,*)
        supertype:  pm#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:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
        supertype:  pm#what_relation (*)
           supertype:  pm#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:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
     supertype:  pm#wnMember (?,?)  member relation in WordNet
        supertype:  pm#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:  pm#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:  pm#binary_relation_with_particular_mathematical_property (?,?)
                 supertype:  pm#relation_with_particular_mathematical_property (*)
                    supertype:  pm#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:  pm#relation__related_thing__relatedthing___related_with  type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type
           supertype:  pm#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:  pm#binary_relation_with_particular_mathematical_property (?,?)
           supertype:  pm#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:  pm#binary_relation_with_particular_mathematical_property (?,?)