W3C home > Mailing lists > Public > http-caching-historical@w3.org > February 1996

Re: source quality, caching, and Vary:

From: Daniel DuBois <ddubois@rafiki.spyglass.com>
Date: Mon, 12 Feb 1996 16:58:17 -0600
Message-Id: <9602122258.AA22720@rafiki.spyglass.com>
To: Paul Leach <paulle@microsoft.com>, http-caching@pa.dec.com
At 01:44 PM 2/12/96 PST, Paul Leach wrote:
>I don't understand how Vary: works where there are different levels of 
>source quality. It would be nice if the source quality of a resource 
>were returned someplace when using Vary: instead of URI:.  Or did I 
>miss something obvious?

There is no source quality with Vary.  Or rather, if there was a source
quality, it's transmittal would be internal to the server and useless to the
receiver.  The idea of Vary: is that it is appropriate only when the server
is unwilling to give both the full details of the variants, and/or unwilling
to use the standard content negotiaion algorithm.  The source quality is
only useful if the standard q*ql*qc*qe*qs algorithm is used.  If a origin
server uses a home-grown algorithm (like if HTTP_USER_AGENT == "Spyglass
Mosaic" then foo else bar) the whole q*ql*qc*qe*qs thing goes out the
window, and hence, qs with it.
Dan DuBois, Software Animal           http://www.spyglass.com/~ddubois/
    Download a totally free copy of the Spyglass Web Server today!
Received on Monday, 12 February 1996 23:22:14 UTC

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