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Re: De Re If-Modified-Since

From: Daniel DuBois <ddubois@spyglass.com>
Date: Thu, 17 Aug 95 10:34:42 -0500
Message-Id: <9508171534.AA22556@hook.spyglass.com>
To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
At 12:49 AM 8/17/95 -0700, Brian Behlendorf wrote:
>I remember you (and/or Rob McCool) proposed just doing a straight string
>compare of the LM and IMS (LM = IMS), which is *different* than LM < IMS <
>CURRTIME.  If you implemented the latter in the Netsite, the Apache group
>will put it in Apache, I bet Chuck would put it in Webstar and Henrik would
>put it in CERN and Brandon would put it in NCSA.  Deal?  I honestly think we
>would address the most serious aspects of the incorrect-time problem without
>forcing a change to the HTTP protocol by doing this. 

I quote myself:
>The spec only refers to "if the resource has been modified since the
>If-Modified-Since: date".  As far as I'm concerned, if the request contains
>"If-Modified-Since: Mon, 14 Aug 1995 23:38:43 GMT", and the server has a
>last modified date of "Mon, 14 Aug 1995 23:38:42 GMT", then returning
>something other than 304 is a BUG.  Who knows how the caching client/proxy
>is saving the date.  Maybe it's saving the last time it requested it, maybe
>it's saving the Date: the server previously sent back, maybe it's saving the
>last time when the response is completely received...

maybe it's saving the Last-Modifed-Date: like everyone here says it
"should."  Maybe not.  It's not the server's place to force the client to
store that information.  The construct as it is simple.  Has this URL
changed since X.  And as Roy pointed out, this construct also had in mind
the idea of functionality to say: "give me something if it less than 15
minutes old".  If-Modifed-SINCE really does mean If-Modified-SINCE.

>If-Different: Date > DATE; Content-length != SIZE; Content-type != text/html;
>where the conditions are OR'd, and quantities are compared (so we can 
>still have the functionality of IMS  where LM < IMS < CURRTIME).  
>Hopefully the syntax could allow queries like "give it to me if it's a 
>larger file" or "give it to me if it's a higher level of HTML" or 

Where's that darn sledgehammer?  I need to swat this fly.
Dan DuBois, Software Animal                          ddubois@spyglass.com
(708) 505-1010 x532                     http://www.spyglass.com/~ddubois/
Received on Thursday, 17 August 1995 08:37:17 UTC

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