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From "Roy T. Fielding" <>
Subject Re: very rough caching change patch - centralize vary/http knowledge
Date Wed, 07 May 2008 17:01:31 GMT
On May 7, 2008, at 9:25 AM, Dirk-Willem van Gulik wrote:

> But to me allowing caching modules some knowledge of HTTP is  
> probably good - as
> optimizing the generic case is simply not worthwhile - the very  
> point of caches
> is that they understand something of the biz-processes to go beyond  
> what a the
> operating system and what not can yield.

Please keep in mind that Vary is an instruction from the origin  
server to
external caches that it does not control.  A cache within an origin  
or reverse proxy/gateway is free to ignore Vary if so configured.   
Thus, an
internal cache may have two sets of instructions -- one "internal vary"
that guides its operation and another Vary header field that is intended
for external recipients of a message.


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