Relation pm#quaternary_relation__quaternary_only_relation (?,?,?)  relation with a fixed arity equal to 4
  exclusion:  binary_relation  ternary_relation  relation_with_variable_arity
  subtype:  subst
  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