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Re: HTTP Caching Model?

From: Daniel W. Connolly <connolly@hal.com>
Date: Thu, 15 Dec 1994 19:03:22 -0600
Message-Id: <9412160103.AA06876@ulua.hal.com>
To: Ari Luotonen <luotonen@neon.mcom.com>
Cc: fielding@avron.ICS.UCI.EDU, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
In message <199412160001.QAA09663@neon.mcom.com>, Ari Luotonen writes:
>
>> Why is that such a bad thing? The server can give a lot of information
>> about what's available by giving several URI: headers.
>
>Hmmm, I don't necessarily support this -- this wastes bandwidth.

I agree. But I didn't say the server should or must; just that it may.

The only thing that it _must_ do is issue _some_ URI: header with 
a vary parameter if it's got variants. That's enough to prevent
proxies from jumping to conclusions.

>Besides, the set of available versions may vary, so the proxy can
>never be sure if it has all the presentations/knowledge of them
>without going to the original server.

If the server gives an Expires: header, the proxy can conclude that
the variants are stable until then. Otherwise, the usual hueristics
apply.

See:
	http://www.hal.com/%7Econnolly/drafts/formalism.html

for details.

Dan
Received on Thursday, 15 December 1994 17:08:44 EST

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