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Re: SHOULD vs MUST (was Re: Review of draft-ietf-geopriv-http-location-delivery-07)

Iljitsch van Beijnum <iljitsch@muada.com> Wed, 25 June 2008 07:30 UTC

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From: Iljitsch van Beijnum <iljitsch@muada.com>
To: Lawrence Conroy <lconroy@insensate.co.uk>
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Subject: Re: SHOULD vs MUST (was Re: Review of draft-ietf-geopriv-http-location-delivery-07)
Date: Wed, 25 Jun 2008 09:30:14 +0200
References: <20080525020040.4DE5A5081A@romeo.rtfm.com> <F66D7286825402429571678A16C2F5EE03ADF950@zrc2hxm1.corp.nortel.com> <20080620195947.29D0B5081A@romeo.rtfm.com> <9D9CF008-7350-4831-8F21-E08A0A7B255E@insensate.co.uk>
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On 21 jun 2008, at 15:31, Lawrence Conroy wrote:

> the SHOULD means "do this unless...",
> and the last phrase covers the "unless".

> I had read 2119 to mean that a MUST was unconditional
> - do this or be non-complaint.
> Do you believe that MUST can have an "unless" clause?
> Doesn't this mean that any SHOULD with an explicit "unless" will
> need to be changed into a MUST - could you expand on this, please?

The difference is that with a SHOULD, the reader may come up with her  
own "unless".

Also note the difference between the two sides in a client-server  
protocol. I recently used SHOULD where I would have liked to use MUST  
but existing clients don't conform to the MUST so I used SHOULD to  
indicate that servers must support clients that don't have the feature.
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