Re: Use of LWSP in ABNF -- consensus call

Julian Reschke <julian.reschke@gmx.de> Mon, 14 May 2007 20:56 UTC

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Date: Mon, 14 May 2007 22:55:54 +0200
From: Julian Reschke <julian.reschke@gmx.de>
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To: Lisa Dusseault <lisa@osafoundation.org>
Subject: Re: Use of LWSP in ABNF -- consensus call
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Lisa Dusseault wrote:
> 
> The IESG reviewed 
> <http://www.ietf.org/internet-drafts/draft-crocker-rfc4234bis-00.txt> 
> for publication as Internet Standard and would like to know if there is 
> consensus to recommend against the use of LWSP in future specifications, 
> as it has caused problems recently in DKIM and could cause problems in 
> other places.
> 
> Some discussion on this point already:
>  - http://www1.ietf.org/mail-archive/web/ietf/current/msg46048.html
>  - http://www1.ietf.org/mail-archive/web/discuss/current/msg00463.html
>  - http://mipassoc.org/pipermail/ietf-dkim/2007q1/007295.html
>  - 
> https://datatracker.ietf.org/public/pidtracker.cgi?command=view_comment&id=66440  
> (in this tracker comment, Chris Newman recommended to remove LWSP, but 
> for backward-compatibility it's probably better to keep it and recommend 
> against use)

I agree that LWSP can be problematic. As the LWSP rule only appears in 
appendix B, the best approach IMHO would be to either leave it in, and 
have a warning explaining the potential problems close to it, or remove it.

The latter sounds simpler, but could cause spec writers that use ABNF to 
just copy the LWSP rule from RFC4234, ignoring the potential issues with it.

The proposed solution to warn about it in the front matter doesn't seem 
to be a good idea due to locality reasons. If there are reasons to avoud 
LWSP, they should be stated close to the definition. If this means we 
need a new revision of the spec, and last-call it again, so be it. No 
reason to hurry.

Best regards, Julian