W3C home > Mailing lists > Public > w3c-dist-auth@w3.org > April to June 2002

etags in If: headers (was: 54th IETF Meeting Information, and RFC2518 open issues)

From: Greg Stein <gstein@lyra.org>
Date: Wed, 24 Apr 2002 23:39:45 -0700
To: "Webdav WG (E-mail)" <w3c-dist-auth@w3c.org>
Message-ID: <20020424233944.A6025@lyra.org>
On Mon, Apr 22, 2002 at 06:53:34PM +0200, Stefan Eissing wrote:
> Am Montag den, 22. April 2002, um 18:36, schrieb Lisa Dusseault:
>...
> If headers with ETags do not add any value to the protocol. For
> GET rfc2616 already defines If-Match and friends. Since the ETag
> only captures content changes (property changes have undefined
> effect on ETags), IF headers for ETag lack a use case.

An etag in an If: header can be used to assert that a file has been
unchanged since you last fetched it. Specifically, that you still have the
locktoken *or* (you lost it and) it is unchanged.

This is to cover the case where lock a file, fetch it, and then attempt to
PUT the file back. The PUT should succeed if you have the locktoken *or* if
you lost your lock but the etag matches what you GET'd (thus: nobody else
changed it).

Arguably, the semantic could be manufactured with other combinations, but
I'd suggest that is your use case.

Cheers,
-g

-- 
Greg Stein, http://www.lyra.org/
Received on Thursday, 25 April 2002 02:38:38 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 2 June 2009 18:44:00 GMT