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Re: DATE-IF-MODIFIED

From: Ross Patterson <Ross_Patterson@ns.reston.vmd.sterling.com>
Date: Mon, 8 Sep 97 11:31:38 EDT
Message-Id: <199709081535.AA29047@reston.vmd.sterling.com>
To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
jg@pa.dec.com (Jim Gettys) writes:

>"Note: An HTTP client should expect that If-Modified-Since headers sent
>for cache validation will be interpreted

"... by the origin server and all intervening proxy servers ..." or words
to that effect

>                                         as
>'If-Modification-date-does-not-match-exactly'.

Let's not introduce the expectation of an "If-Modification-date-..."
header-field and associated semantics.  Rephrasing that to read "... as
requesting an exact match between the supplied HTTP-date and the last
modification date and time of the resource ..." or something like it
would do the job.

>                                               In other words, an HTTP client
>should preserve all of the accuracy in the Last-Modified date,

It's not just a date, so how about "HTTP-date" instead.

>                                                               rather than
>(perhaps) playing games based on the official semantics of If-Modified-Since."

Let's stop after "... in the Last-Modified date" and delete the remainder
of the sentence.  That way we wind up with a normative statement, rather
than one that calls into question the motivation of the change or limits
the interpretation of its scope.

To summarize the above, here's my suggested replacement:

   "Note: An HTTP client should expect that If-Modified-Since headers
   sent for cache validation will be interpreted by the origin server
   and all intervening proxy servers as requesting an exact match
   between the supplied HTTP-date and the last modification date and
   time of the resource.  In other words, an HTTP client should preserve
   all of the accuracy in the Last-Modified HTTP-date."

Ross Patterson
Sterling Software, Inc.
VM Software Division
Received on Monday, 8 September 1997 08:35:38 EDT

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