Relation pm#same_type_as (type,type)
  subtype: {equivalent_class equivalent_property}
  equal:  equal (pm)
  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:  same_as (?,?)  MORE PRECISE TYPES THAN THIS ONE SHOULD BE USED
     supertype:  equal (?,?)  "=" in KIF; true if the 1st argument is identical to the 2nd
        supertype:  equivalence_relation__equivalencerelation (?,?)  this category only serves structuration purposes: it is instance of pm#equivalence_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:  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:  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 (?,?)