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RE: [bug report] refreshing file from remote

From: Dave J Woolley <DJW@bts.co.uk>
Date: Wed, 18 Aug 1999 13:37:14 +0100
Message-ID: <81E4A2BC03CED111845100104B62AFB53F3C23@stagecoach.bts.co.uk>
To: www-amaya@w3.org
> I suspect the refresh test was
>         if  ispfiledate_time > cacheversiondate_time  then update
> while it should be 
>        if   ispfiledate_time <> cacheversiondate_time then update
> 
	Because Expires is the exception rather than the
	rule in HTTP 1.0, most caches need to do a > rather
	than an equality date, because they typically do
	(last_modified + 0.2 * ( date - last_modified)) as
	their estimate of the expiry date.  Any HTTP 1.0 server
	with a wild time will not work well with CERN or Squid
	caches and probably most others.

	HTTP 1.1 replaces Expires with Cache-Control: max-age.
	This is relative to the Date header value and can only
	meaningfully be tested with inequality tests.

	I assume that Amaya uses If-Modified-Since requests to
	actually check for updates, and therefore it is the
	Server (or public proxy) that does the comparison.  
	The one thing to beware
	of is that the I-M-S values should be the value from the
	L-M-S header on the original page, not the Date header and
	certainly not the clients idea of the time it received the
	page.
Received on Wednesday, 18 August 1999 08:39:25 UTC

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