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Change to Vary header requirements

From: Koen Holtman <koen@win.tue.nl>
Date: Fri, 7 Jun 1996 01:39:30 +0200 (MET DST)
Message-Id: <199606062339.BAA01545@wsooti01.win.tue.nl>
To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com, koen@win.tue.nl
Cc: Koen Holtman <koen@win.tue.nl>

In todays editorial group phone conference, we discussed again the
rule on when to include a Vary header in a response.

This rule is mentioned a number of times in the spec.  It is first
mentioned in Section 12.1:

#HTTP/1.1 origin servers MUST include an appropriate Vary header field
#(section 14.43) in any response based on server-driven negotiation.

We decided to change the rule into

#HTTP/1.1 origin servers MUST include an appropriate Vary header field
#(section 14.43) in any cachable response based on server-driven
#negotiation.           ^^^^^^^^

because there is no need, from a correctness standpoint, to include a
Vary header field in un-cachable responses.  It may be nice for some
user agents to see a Vary in un-cachable responses (see Section 15.7),
but this does not warrant a MUST.

This change mainly intends to ease the writing, or the porting to 1.1
servers, of CGI scripts that generate un-cachable (dynamic) responses.
With the new text, the authors of such scripts won't have to spend
time close-reading section 12 in order to figure out what to put in
the Vary header.

Koen.
Received on Thursday, 6 June 1996 16:41:52 EDT

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