Relationpm#quaternary_relation__quaternary_only_relation(?,?,?)relation with a fixed arity equal to 4exclusion: pm#binary_relation pm#ternary_relation pm#relation_with_variable_arity subtype: kif#subst supertype: pm#relation_with_particular_property (*)this rather fuzzy type permits to group categorization schemes less common than those covered by the previous sibling categoriessupertype: pm#relation__related_thing__relatedthing___related_with (*)type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type