[9067] in www-talk@info.cern.ch
Re: Caching policy?
daemon@ATHENA.MIT.EDU (N.G.Smith)
Fri Sep 1 05:44:29 1995
To: www-talk@w3.org
In-Reply-To: Your message of "Fri, 01 Sep 1995 10:00:08 +0100."
<9509011000.aa14255@salmon.maths.tcd.ie>
Date: Fri, 01 Sep 1995 09:42:57 +0000
From: "N.G.Smith" <ngs@sesame.hensa.ac.uk>
Resent-From: www-talk@w3.org
>Is there a recommended caching policy for proxies? The algorithm that
>suggests itself to me is to check the expiry date for the cached document
>and if it's still in date use it, otherwise send a conditional GET.
If every document arrived with an expiry date then this would be fine.
Unfortunately precious few do and so other heuristic rules are often
used to guess when a conditional GET is required. The rule most
commonly used is based on a proportion of the time since the document
was Last-Modified. This assumes that a recently modified document is
likely to change again soon, while a document that has not been touched
in ages will remain fairly static. A maximum upper bound is often used
to make sure that conditional GETs happen on a regular basis even if
the Last-Modified date was a long time ago.
>I assume that there have been discussions of this: is there a reference to
>a summary anywhere?
>
>Colman
Discussion of these issues used to happen on www-proxy@w3.org, but the
list of Mailing Lists at W3C [1] suggests that www-proxy is `previous'
rather than `current'. Archives of the list only exist to January 1995.
Has the list been discontinued?
Neil Smith
HENSA Unix
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[1] http://www.w3.org/hypertext/WWW/Mail/Lists.html
