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Re: i37: Vary and non-existant headers

From: Mark Nottingham <mnot@mnot.net>
Date: Tue, 29 Jul 2008 08:13:03 +0100
Cc: "'HTTP Working Group'" <ietf-http-wg@w3.org>
Message-Id: <58FB3053-79ED-4D19-9237-A16FC5BE2AE4@mnot.net>
To: Brian Smith <brian@briansmith.org>

On 28/07/2008, at 6:35 PM, Brian Smith wrote:

> Mark Nottingham wrote:
>> http://tools.ietf.org/wg/httpbis/trac/ticket/37
>> Roy sort-of proposed deleting "present" in
>> <http://lists.w3.org/Archives/Public/ietf-http-wg/2006OctDec/ 
>> 0090.html
>> In addition, I'd propose:
>> * adding: "When a resource's representations vary, an origin
>> server SHOULD include the Vary header even when the selecting
>> header(s) are not present; otherwise, caches will use that
>> representation inappropriately."
> I think it would be better to say: "For each request URI, an origin  
> server
> SHOULD return the same Vary header field value for every request."  
> In this
> way, the Vary header is not just a response header but a "resource  
> header".

That is exactly how Vary doesn't work, and the interpretation that  
we're trying to avoid.

>> * adding: "Caches MAY canonicalise request headers before
>> comparing them for purposes of determining whether they match
>> during variant selection."
> Clients, intermediaries, and servers should always be able to  
> canonicalize
> headers in any situation. Putting a specific statement about it here  
> imples
> there are some cases in which canonicalization is not allowed. I  
> suggest
> leaving this part out.

Enough people have had questions about this that it's worthwhile  
calling out explicitly, AFAICT.


Mark Nottingham     http://www.mnot.net/
Received on Tuesday, 29 July 2008 07:13:40 UTC

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