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

John C Klensin <john-ietf@jck.com> Fri, 18 May 2007 01:14 UTC

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Date: Thu, 17 May 2007 21:14:21 -0400
From: John C Klensin <john-ietf@jck.com>
To: Harald Tveit Alvestrand <harald@alvestrand.no>, Sam Hartman <hartmans-ietf@mit.edu>
Subject: Re: [ietf-dkim] Re: Use of LWSP in ABNF -- consensus call
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--On Thursday, 17 May, 2007 21:52 +0200 Harald Tveit Alvestrand
<harald@alvestrand.no> wrote:

> I don't agree with the meaning I get from this statement. The
> problem is that the construct that ABNF calls "LWSP" causes
> problems in protocols that use it.
> This problem is independent of the name of the construct; the
> problem is in defining a grammar where the sequence
> <CRLF><CRLF> has a different meaning than <CRLF><SPACE><CRLF>.
>...

Interesting.  I don't think that is a problem with the grammar,
and think it would be rather hard to define a grammar that would
not permit that situation.   After all
    <CRLF> Thing <SPACE><CRLF> could case similar problems if
some construction permitted it and defining a grammar that would
prohibit any <SPACE><CRLF> construction isn't easy in ABNF for
reasons that have nothing to do with LWSP.

Instead, I see the problem as using the grammar to define
situations equivalent to 
    LWSP [ optional-stuff ] CRLF
as compared to 
    LWSP AtLeastOneRequiredThing CRLF
or
    [ LWSP optional-stuff ] CRLF

I don't see either of the latter as problematic.

      john

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