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Re: draft-snell-http-prefer

From: Mark Nottingham <mnot@mnot.net>
Date: Wed, 3 Oct 2012 16:41:02 +0100
Cc: James M Snell <jasnell@gmail.com>, ietf-http-wg@w3.org
Message-Id: <E407DC0F-921E-42BE-8AD1-B0D03C08F933@mnot.net>
To: Ken Murchison <murch@andrew.cmu.edu>
If the response has changed based upon the Prefer header, you really need to include Vary: prefer.

If you can infer from that what the server did, there's no need for a separate header.


On 03/10/2012, at 4:14 PM, Ken Murchison <murch@andrew.cmu.edu> wrote:

> Hi James,
> That would obviously work.  Is reusing the Vary header not a good idea?
> James M Snell wrote:
>> A much older version of the specification included an optional Preference-Applied response header that could explicitly indicate whether a particular preference was applied, but after lots of feedback that "I wasn't going to need it", I pulled it back out (largely against my better judgement). I'm thinking that perhaps it needs to be added back in. - James
>> On Wed, Oct 3, 2012 at 7:27 AM, Ken Murchison <murch@andrew.cmu.edu <mailto:murch@andrew.cmu.edu>> wrote:
>>    Hello,
>>    I'm working on draft draft-murchison-webdav-prefer which describes
>>    how the return-minimal and return-representation apply to
>>    WebDAV/CalDAV methods.  My work is primarily CalDAV-centric but we
>>    are trying to make it generic to WebDAV and its derivatives.
>>    One of the issues that keeps coming up is a way for the client to
>>    differentiate between two  cases:
>>    - the server doesn't return a representation because it ignored or
>>    doesn't support the return-representation preference
>>    - the server understood the preference but didn't return a
>>    representation because it didn't change from what was in the request
>>    One possible solution is for the server to return a Vary: Prefer
>>    header to indicate that the server understood the preference,
>>    thereby allowing the client to infer what the lack of a
>>    representation in the response means.
>>    The next question is, does any such mandate or recommendation, if
>>    required, belong in my webdav-prefer draft or in the base Prefer spec?
>>    Thoughts?
>>    --     Kenneth Murchison
>>    Principal Systems Software Engineer
>>    Carnegie Mellon University
> -- 
> Kenneth Murchison
> Principal Systems Software Engineer
> Carnegie Mellon University

Mark Nottingham
Received on Wednesday, 3 October 2012 15:41:34 UTC

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