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RE: PROPOSAL: Weak Validator definition [i101]

From: Brian Smith <brian@briansmith.org>
Date: Tue, 29 Jul 2008 13:41:41 -0500
To: "'Julian Reschke'" <julian.reschke@gmx.de>, "'Mark Nottingham'" <mnot@mnot.net>
Cc: "'HTTP Working Group'" <ietf-http-wg@w3.org>
Message-ID: <5ED3859107EF4CC29372BB4B6B67F732@T60>

Julian Reschke wrote:
> Julian Reschke wrote:
> > ...
> > Mark and I discussed this yesterday, and Mark came up with 
> a concrete 
> > proposal (see 
> <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/101>):
> > ...
> 
> Proposed patch: 
> <http://www3.tools.ietf.org/wg/httpbis/trac/attachment/ticket/
> 101/i101.diff>.
> 
> Note this also drops a leading "In order to be legal..." 
> intro -- it's not like we ever talk about entity tags 
> behaving illegally :-)

"entity value" is an undefined term that is only used in this one place, and
it could be interpreted as "entity body" inappropriately. "Entity" would be
better since it is defined as the combination as the entity-header fields
and the entity-body.

I would expect that a validator should change whenever the entity changes,
*and* whenever the entity *headers* change as well. For example, changing
the Content-Type from text/plain to text/html is a significant change even
if the entity body stays the same. Otherwise, because of the restrictions on
304 responses containing entity headers, the client could repeatedly get 304
responses and never learn that the content-type changed. Similarly,
conditional PUTs would unknowingly revert an intermediate change in entity
headers.

For example, an ETag generated as the MD5 of just the entity body would not
be a good ETag, but an ETag generated as the MD5 of the entity headers
together with the entity body would be a good ETag.

- Brian
Received on Tuesday, 29 July 2008 18:42:17 GMT

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