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Re: PUT vs strong ETags

From: Mark Baker <distobj@acm.org>
Date: Wed, 30 Nov 2005 08:02:56 -0500
Message-ID: <c70bc85d0511300502t3e5c8955uedf44957f178a2d3@mail.gmail.com>
To: Henrik Frystyk Nielsen <henrikn@microsoft.com>
Cc: Scott Lawrence <scott@skrb.org>, Julian Reschke <julian.reschke@gmx.de>, HTTP Working Group <ietf-http-wg@w3.org>

On 11/30/05, Henrik Frystyk Nielsen <henrikn@microsoft.com> wrote:
> Having a PUT response include an e-tag associated with the current
> entity is necessary in order to avoid the lost update problem (see [1]).
> I don't think this is a redefinition of the use of e-tags: section
> 10.2.2 states that
> "A 201 response MAY contain an ETag response header field indicating the
> current value of the entity tag for the requested variant just created,
> see section 14.19."

Good find Henrik.  I still think that's suboptimal from the point of
view of providing a *generic* validator which is independent of
response semantics.  If we were addressing the lost update problem
today, I'd be suggesting minting a new response header which could
carry that ETag.

> The use of the term "requested variant" is consistent with the use in
> section 14.19 and elsewhere in the spec. It refers to the resource
> identified by the request URI regardless of the method used.

I'm with Julian on that being non-obvious.


Mark Baker.  Ottawa, Ontario, CANADA.        http://www.markbaker.ca
Coactus; Web-inspired integration strategies   http://www.coactus.com
Received on Wednesday, 30 November 2005 13:20:21 UTC

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