- | Ident_alias of string * string (* identifier, uri *)
- | Symbol_alias of string * int * string (* name, instance no, description *)
- | Number_alias of int * string (* instance no, description *)
+ | Ident_alias of string * string (* identifier, uri *)
+ | Symbol_alias of string * string option * string (* name, uri, description *)
+ | Number_alias of string option * string (* uri, description *)