What about this grammar?

Hello world,

Assuming that ‘^S’ in what follows represents the single character #13,
is an implementation required to, allowed to, or forbidden from
accepting this grammar:

  S = -'^S', 'a'.

parsing “^Sa” to produce <S>a</S>?

(The problem, in case it’s not immediately obvious, is that the grammar
cannot be represented in XML because a #13 isn’t allowed.)

I don’t think there’s any question that

  S = -#13, 'a'.

must be accepted and does what I suggested above.

                                        Be seeing you,
                                          norm

--
Norm Tovey-Walsh
Saxonica