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Re: Still trying to make sense of HTTP caching model

From: John Franks <john@math.nwu.edu>
Date: Wed, 6 Sep 1995 08:45:05 -0500 (CDT)
Message-Id: <199509061345.IAA09268@hopf.math.nwu.edu>
To: Shel Kaphan <sjk@amazon.com>
Cc: mogul@pa.dec.com, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
According to Shel Kaphan:
> 
> Jeffrey Mogul writes:
> 	...
> 
>  >    2.	Cache this object but always validate before using
>  > 	   (i.e., "Expires: 1 January 1900")
> 
> I see. This actually gives a reasonable meaning to this construct.
> This meaning seems better than simply "don't cache this", and works well with
> GET if-<whatever>.  With plain GET it is equivalent to not caching.
> 	...

This usage encodes some very non-intuitive semantics in the Expires:
heading.  If you want to tell the proxy to cache a document but always
validate it then create a header or Pragma to do that.  Trying to
encode this request in an otherwise meaningless variant of an existing
header is a mistake.  This will inevitably lead to confusion because
most people already think they know what Expires: means and they
have a right to think that.

John Franks
Received on Wednesday, 6 September 1995 06:48:07 EDT

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