Re: [ietf-dkim] Re: Use of LWSP in ABNF -- consensus call

Tony Finch <dot@dotat.at> Fri, 18 May 2007 14:23 UTC

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Date: Fri, 18 May 2007 15:23:12 +0100
From: Tony Finch <dot@dotat.at>
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To: John C Klensin <john-ietf@jck.com>
Subject: Re: [ietf-dkim] Re: Use of LWSP in ABNF -- consensus call
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On Fri, 18 May 2007, John C Klensin wrote:
> On Friday, 18 May, 2007 09:00 +0100 Tony Finch <dot@dotat.at>
> wrote:
> >
> > 	NTWSP = [CRLF] 1*WSP ; non-trailing white space
>
> Sure.  Except that much, if not most, of our textual
> descriptions of these protocols describes lines, and line-like,
> constructions as _ending_ in CRLF.  Moving to  "starting in
> CRLF" creates a conceptual difference between prose definition
> and formal syntax, which strikes me as a bad idea.

Don't do that then. The suggestion I made above was for a no-trailing-
whitespace variant of 2822's FWS, and as such it would be used in a
grammar inside a logical line, not at either end. You seem to be inventing
problems that might occur in badly-designed grammars, and as such these
are bugs in the grammars and not due to limitations of ABNF (which, after
all, is equivalent to any other notation for describing context-free
grammars).

> Of course, in the above, since [CRLF] is optional, "1*WSP" alone
> satisfies the production as written and still does not prevent
>    <CRLF> space space space
>    <CRLF>

Um, no, because WSP = SP / HTAB

Tony.
-- 
f.a.n.finch  <dot@dotat.at>  http://dotat.at/
SOUTHEAST ICELAND: CYCLONIC, BECOMING NORTHERLY GALE 8 OR SEVERE GALE 9,
DECREASING 6 OR 7. ROUGH OR VERY ROUGH, OCCASIONALLY HIGH. SHOWERS. MODERATE
OR GOOD.