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Re: draft-snell-http-prefer

From: James M Snell <jasnell@gmail.com>
Date: Wed, 17 Oct 2012 08:09:34 -0700
Message-ID: <CABP7RbcfgPt3j46suLuuTDeQjDgOrcyE+E6pujm5W0HQc35QcQ@mail.gmail.com>
To: Ken Murchison <murch@andrew.cmu.edu>
Cc: "Roy T. Fielding" <fielding@gbiv.com>, Mark Nottingham <mnot@mnot.net>, ietf-http-wg@w3.org
On Wed, Oct 17, 2012 at 5:15 AM, Ken Murchison <murch@andrew.cmu.edu> wrote:

> James M Snell wrote:
> [snip]
>> Noted and agreed.. but that's not quite what's going on with the Prefer
>> header here. The return-representation preference merely indicates to the
>> server that the UA would like the server to return a representation of the
>> resource within the response vs. a representation of the request status.
>> What's missing is some indicator within the response as to which the server
>> is actually returning. There is some ambiguity that needs to be resolved.
>> All the Preference-Applied header does is provide an explicit indicator
>> that the server did, in fact, do as the UA asked and returned the resource
>> representation in the response... an indicator that is only necessary if
>> it's not obvious by the content type of the payload or by direct
>> examination of the payload.
> Actually, the question/concern that started this thread (not my own, but
> channeled from CalConnect) is can a client can figure out why the server
> didn't respond with a representation?  Did the server not understand the
> return-representation preference?  Did it understand it and choose to
> ignore it?  Or did the server not include a representation in the response
> because it didn't change from what the client sent and didn't want to waste
> the bandwidth?
> If you don't think that this is a problem, or don't think its worth fixing
> (I might agree here), then please don't hold up the WGLC if
> Preference-Applied is going to be controversial.
Thanks for chiming in again on it Kenneth. I was going to write this up
last night but ended up getting side tracked by sleep ;-) ... In my view
the Preference-Applied header is entirely optional. There's no demonstrated
harm in having it and it does have a useful (if limited) purpose for the
type of case you've suggested. I understand Mark's argument but I do not
feel the objection is strong enough to warrant holding things up (or making
further modifications to the spec). For those who do not feel the
Preference-Applied header is necessary, they needn't worry about it as it
can safely be ignored. For those who find it useful, it's there. Time and
implementation will ultimately determine whether it was truly necessary.

- James

> --
> Kenneth Murchison
> Principal Systems Software Engineer
> Carnegie Mellon University
Received on Wednesday, 17 October 2012 15:10:30 UTC

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