Re: Syntax

Julian Reschke <julian.reschke@gmx.de> Tue, 09 January 2007 08:01 UTC

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To: Stephane Bortzmeyer <bortzmeyer@nic.fr>
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Subject: Re: Syntax
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Stephane Bortzmeyer schrieb:
> On Mon, Jan 08, 2007 at 10:31:14AM +0100,
>  Julian Reschke <julian.reschke@gmx.de> wrote 
>  a message of 48 lines which said:
> 
>> Choosing characters for identifiers: again, just borrow from
>> somewhere else, such as <http://www.w3.org/TR/REC-xml/#NT-Name>).
> 
> Did anyone already tried to convert it in ABNF? The production
> BaseChar in the XML standard is a bit frightening and may exercice the
> limits of some programs. Implementation reports are welcome.
> 
> Otherwise, what do you think of the solution used in RFC 4646?
> 
>    ASCCHAR    = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26
>    UNICHAR    = "&#x" 2*6HEXDIG ";"

The reason why XML's production is complex is that it excludes 
characters that do not belong into identifiers.

The escaping rule quoted above doesn't solve that problem at all; it's 
just an escaping rule.

>> I think inventing a new format, but not taking I18N is very hard to
>> defend. As far as I can tell, there's no real chance to get it
>> published.
> 
> Hmmm, how many IETF formats are in Unicode? (Apart from those based
> only on XML, like Atom in RFC 4287.) ABNF is not, for instance (right,
> it is not a few format, the RFC is recent but it derives from an older
> format.)

I just tried to understand how RFC4234 works with non-ASCII characters, 
and it's not obvious at all. Section 2.4 seems to deal with it but 
really sounds a bit like hand-waving.

Best regards, Julian


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