Re: New draft (Was: I-D ACTION:draft-klensin-unicode-escapes-00.txt

["Clive D.W. Feather" <[e-mail]>]

John C Klensin said:
> 	* I have not touched the ABNF associated with the \u /
> 	\U case.  I have inserted an explicit placeholder but,
> 	as discussed on this list, I think we need to figure out
> 	what we want to do and then go back and adjust the
> 	metalanguage productions.   In particular, there has
> 	been one strong suggestion, with which I agree, that we
> 	not take the obvious approach of substituting %x5C.75
> 	for "\u", since the intent is a character string
> 	abstraction (independent of the implementation character
> 	set) rather than specific octets.

I asked Paul Overell about this and got the following answer (in part):

>        "By separating external encoding from the syntax, it is intended
>        that alternate encoding environments can be used for the same
>        syntax."
>
> So although "\" means us-ascii %x5C, the same ABNF may still be used to
> specify the syntax of strings expressed in a different character set by
> specifying the mapping between %x5C and the encoding used, but that is
> outside the scope of ABNF.
   
In other words, you write the ABNF as if the target encoding was ASCII, but
then state somewhere in the document that other encodings may be used and
the ABNF is meant to represent the abstract characters, not specific octet
values.

Or else we either drop ABNF (wrong, I think) or state explicitly that the
notation is "ABNF except for case-sensitivity".

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