W3C home > Mailing lists > Public > ietf-http-wg-old@w3.org > May to August 1995

Re: Improving If-Modified-Since

From: Roy Fielding <fielding@beach.w3.org>
Date: Tue, 15 Aug 1995 18:03:01 -0400
Message-Id: <199508152203.SAA32719@beach.w3.org>
To: Lou Montulli <montulli@mozilla.com>
Cc: hartill@lanl.gov, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
>> As Roy says, fix that and most of the problems will go away.
>
>"fix" is an interresting choice of words.  "change" is more appropriate.
>Not sending an "if-modified-since" header with reloads would be extremely
>costly in terms of bandwidth.  Adding cache checksums is a much better 
>solution.

Browser semantics -- not defined by any spec, but well known enough
that I can say with absolute certainty that this is a bug in Navigator.

If the user requests a "Reload" operation, they are asking for a
new copy of the resource from its origin.

Sending IMS prevents a new copy being generated by the origin server.

So, don't send IMS when the user hits the Reload button! 

Believe me, nobody is more concerned about network bandwidth and
caching than I am.  However, caching only works if the user is
in control of the cache, not the other way around.  This has
less significant impact on bandwidth than do the thousands of hopeless
attempts to override this behavior by current Navigator users.

 ....Roy T. Fielding  Department of ICS, University of California, Irvine USA
                      Visiting Scholar, MIT/LCS + World-Wide Web Consortium
                      (fielding@w3.org)                (fielding@ics.uci.edu)
Received on Tuesday, 15 August 1995 15:05:21 EDT

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