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RE: Cache-Control and Pragma

From: Larry Masinter <masinter@parc.xerox.com>
Date: Thu, 10 Dec 1998 08:50:07 PST
To: "Nottingham, Mark (Australia)" <mark_nottingham@exchange.au.ml.com>
Cc: <http-wg@hplb.hpl.hp.com>
Message-Id: <000e01be245d$244ae880$d411020d@copper.parc.xerox.com>
Mark Nottingham wrote:

> I can't find anything in the Draft that addresses the situation when
> both Cache-Control and Pragma: no-cache headers are set, and they are in
> conflict. 
> For instance, if I use
> 
> Cache-Control: must-revalidate
> Pragma: no-cache
> 
> on a HTTP response, it would be desireable to have it cached (and always
> revalidated) by HTTP 1.1 caches, and not cached by HTTP 1.0 caches.
> However, I can see nothing in the Draft about this, and some
> implementations, upon reading 14.32 Pragma, might never cache the
> object. While the action is safe, it's not ideal.
>  
> Am I missing something somewhere? Thanks.

The interaction of headers whose interaction is not specified
is not specified.

An origin server cannot depend on the precedence of
"Cache-Control: must-revalidate" and "Pragma: no-cache",
and a server (1.0 or 1.1) might ignore either or both.

Larry
-- 
http://www.parc.xerox.com/masinter
Received on Thursday, 10 December 1998 16:55:22 EST

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