Re: i37: Vary and non-existant headers

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

> Mark Nottingham wrote:
>> Roy sort-of proposed deleting "present" in
>> < 
>> 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

Received on Tuesday, 29 July 2008 07:13:40 UTC