Function pm#complement_class (class -> class)  if something is not in one of the classes, then it is in the other, and vice versa; in WebKB, use the link '/'
  equal:  complement_of (pm)
  supertype:  exclusive_class__exclusiveclas (class,class)  the 2 classes have no common subtype/instance; in WebKB, use the link '!'
     supertype:  relation_to_another_class (class,class+)
        supertype:  relation_from_class_to_collection (class,collection)
           supertype:  relation_from_type_to_collection (type,collection)
              supertype:  relation_between_collections (collection,collection+)
                 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:  relation_to_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
                    supertype:  what_relation (*)
              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_class (class,*)
              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_to_another_set_or_class (set_or_class,set_or_class+)  this category is needed to group SUMO relations between classes which cannot be subtype of pm#relation_from_type because their signatures curiously also involve sets
           supertype:  relation_between_collections (collection,collection+)
           supertype:  relation_to_set_or_class (*,set_or_class)
              supertype:  relation_to_collection (*,collection)
     supertype:  disjoint (set_or_class,set_or_class)  like sumo#disjoint but from a a pm#set_or_class to another
        supertype:  relation_to_another_set_or_class (set_or_class,set_or_class+)  this category is needed to group SUMO relations between classes which cannot be subtype of pm#relation_from_type because their signatures curiously also involve sets
     supertype:  exclusive_type__exclusivetype (type,type)  in WebKB, use the '!' link
        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:  different__different_from__differentfrom (?,?)
        supertype:  irreflexive_relation__irreflexiverelation (?,?)  this category only serves structuration purposes: it is instance of pm#irreflexive_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:  symmetric_relation__symmetricrelation (?,?)  this category only serves structuration purposes: it is instance of pm#symmetric_relation_type which is not instance of pm#class_of_inheritable_relation_type
           supertype:  binary_relation_with_particular_mathematical_property (?,?)
        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:  complement_type (type -> type)  a supertype of owl#complement_of which can only connect RDFS/OWL classes
     supertype:  closed_exclusion (type -> type)  the '/' link in the FT notation:  the two linked types either are respectively identical to pm#thing and pm#nothing (they are "complement types") or they subtype a same type and form a complete subtype partition
        supertype:  exclusive_type__exclusivetype (type,type)  in WebKB, use the '!' link