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EDITS for Section 13.20 (Cache Replacement for Varying Resources)

From: Koen Holtman <koen@win.tue.nl>
Date: Sun, 28 Apr 1996 18:41:51 +0200 (MET DST)
Message-Id: <199604281641.SAA05207@wsooti04.win.tue.nl>
To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Cc: Koen Holtman <koen@win.tue.nl>

Here is new text for the cache replacement section.  The change-bars
are computer-generated.  These changes reflect the removal of opaque
selecting validators from the spec.  

To Jim Gettys: please perform the edits indicated below as soon as you
can.  Also, delete Section 13.12 (cache keys), except for sub-section
13.12.4 (Canonicalization of URIs), which should be merged with
Section 3.2.2 (http URL).

Koen.

--snip--


   13.20 Cache Replacement for Varying Resources

   If a new 200 (OK) response is received from a non-varying resource
   while an old 200 (OK) response is cached, caches can delete this old
   response from cache memory and insert the new response.  For 200 (OK)
|  responses from varying resources (Section 10.vary), cache replacement
   is more complex.

   HTTP/1.1 allows the authors of varying resources to guide cache
|  replacement by the inclusion of variant-IDs in the responses of these
|  resources. [##lots of complexity deleted here##] If a cache has
|  stored in memory a 200 (OK) response with a certain variant-ID, and
   receives, from the same resource, a new 200 (OK) response which has
|  the same variant-ID, this should be interpreted as a signal from the
   resource author that the old response can be deleted from cache
   memory and replaced by the new response.

|  The variant-ID mechanism cannot cause deletion from cache memory of old
|  responses with variant-IDs that will no longer be used.  It is expected
   that the normal 'least recently used' update heuristics employed by
   caches will eventually cause such old responses to be deleted.

|  All responses from varying resources SHOULD include variant-IDs.  If
|  these are not present, the resource author can expect caches to
|  correctly handle requests on the varying resource, but cannot expect
|  the caching to be efficient.
Received on Sunday, 28 April 1996 09:48:06 EDT

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