Relationpm#injective_binary_relation(?,?)if P is injective, then if P(x,y) and P(z,y) then x=z; e.g., if nameOfMonth(m,"Feb") and nameOfMonth(n,"Feb") then m and n are the same month; this category only serves structuration purposes: it is instance of pm#injective_binary_relation_type which is not instance of pm#class_of_inheritable_relation_typetype: pm#injective_binary_relation_typeif P is injective, then if P(x,y) and P(z,y) then x=z; e.g., if nameOfMonth(m,"Feb") and nameOfMonth(n,"Feb") then m and n are the same monthsupertype: 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 categoriessupertype: pm#relation__related_thing__relatedthing___related_with (*)type for any relation (unary, binary, ..., *-ary) and instance of pm#relation_type