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Re: ADAMS1, point 31. (cachability of methods).

From: Henrik Frystyk Nielsen <frystyk@w3.org>
Date: Mon, 16 Nov 1998 16:27:05 -0500
Message-Id: <3.0.5.32.19981116162705.02ebd420@localhost>
To: Jeffrey Mogul <mogul@pa.dec.com>, http-wg@hplb.hpl.hp.com
At 12:32 11/16/98 PST, Jeffrey Mogul wrote:

>If the origin server is using an extension that does require
>write-through, then it shouldn't be sending responses with
>something like:
>	Cache-control: max-age=12345
>which implies cachability.  In the case you're describing, the
>origin server has to send something like
>	Cache-control: max-age=12345, must-revalidate
>or
>	Cache-control: max-age=0, must-revalidate
>to get the right semantics.

This is different from the cache semantics that I am after.

There is a large group of extensions which your proposed change will
impact:  the group of extensions describing under which terms a cached
entry can be handed out based on payment, copyright, licensing, content
filtering, added service, etc.

If the cache knows about one of these mandatory extensions (using the M-
prefix) then it should be able to serve the request without revalidating
the response. Imagine if 80% of requests are M- prefixed with some widely
used copyright extension then the forced revalidations are potentially
seriously impacting cache performance without reason.

True, caches that don't understand the extension will have to validate but
on the other hand, if the extension is fully cachable by everyone then it
hardly calls for messing with the method name but instead for an optional
extension. There is no need to produce more than one GET method.

I do not believe we at this point can change whether we consider caching or
the method to be the highest in the hierarchy.

Henrik
--
Henrik Frystyk Nielsen,
World Wide Web Consortium
http://www.w3.org/People/Frystyk
Received on Monday, 16 November 1998 21:27:37 EST

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