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Re: Summary of opinions on Negotiate header

From: Larry Masinter <masinter@parc.xerox.com>
Date: Thu, 26 Sep 1996 15:09:44 PDT
To: koen@win.tue.nl
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <96Sep26.150944pdt."2757"@golden.parc.xerox.com>
X-Mailing-List: <http-wg@cuckoo.hpl.hp.com> archive/latest/1648
> While most of this discussion boils down to a question of taste, there
> *is* a real technical argument against stuffing `n/t' into the Accept
> header: saying `Vary: Accept, Accept-Language' in stead of `Vary:
> Negotiate, Accept-Language' will greatly reduce the efficiency of Vary
> header based caching.

I'm really confused by something, but I'm having trouble working it
out.  Let's suppose the Vary header in the response only notes the
request headers that the resource _actually_ varies on, whether or not
client does transparent negotiation. I'm going to use <negotiable> for
a bit to designate the indicator, since I don't like "n/t" much:

If the resource only varies on language and not media type,
the request says
   Accept: <negotiable>
Case a:
  response includes
   Vary: Accept-Language
  and a body that's the best guess about language.
  will the cache ever return the wrong result?
case 1:
   Accept-Language is the same.
     Cache will return the same document. But this is the right
     'best guess', isn't it?
case 2:
   Accept-Language is different.
      Cache won't match.

So why do you need Vary: Negotiate at all? (suggestions on
<negotiable> later).

Received on Thursday, 26 September 1996 15:20:48 UTC

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