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Re: Expires, Last-Modified, Pragma: no-cache etc.

From: Shel Kaphan <sjk@amazon.com>
Date: Fri, 18 Aug 1995 13:56:14 -0700
Message-Id: <199508182056.NAA00534@bert.amazon.com>
To: Koen Holtman <koen@win.tue.nl>
Cc: fielding@beach.w3.org, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Koen Holtman writes:
 > Jean-Philippe Martin-Flatin:
 > > What do we gain by having both a
 > >'no-cache' and a 'private' Pragma in terms of functionality ? A 'shared
 > >response cache' is basically a proxy/cache, and Pragma is meaningful to
 > >proxies only, not to user agents. So both headers really mean "don't cache
 > >this response in a proxy/cache", and both let a user-agent local cache free
 > >to cache the response or not.
 > 
 > Pragma: private would instruct a user agent not to cache the response if its
 > cache memory (say part of a harddisk in an MS-DOS pc in a university PC lab)
 > is publicly accessible.  This is particularly important for user agents that
 > do not clear their caches at the end of the session.
 > 
 > Of course, the user agent needs to be configured to know that its cache is
 > publicly accessible, one could have a configuration option like `cache
 > private responses on local disk?'.
 > 
 > >Jean-Philippe
 > 
 > Koen.

This explanation is a little different from others floating around.
The other interpretation is that Private means that no other
user-agent should be allowed to access a cached copy of this document,
which would presumably mean that it should not be cached in any
intermediate proxy (except possibly for use by the originally
requesting user-agent, but that's too hard and not very useful).

--Shel
Received on Friday, 18 August 1995 14:00:56 EDT

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