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RE: getlastmodified of collections

From: Julian Reschke <julian.reschke@gmx.de>
Date: Sat, 6 Sep 2003 11:46:28 +0200
To: "Lisa Dusseault" <lisa@xythos.com>, "'Julian Reschke'" <julian.reschke@gmx.de>, "'Nevermann, Dr., Peter'" <Peter.Nevermann@softwareag.com>, <w3c-dist-auth@w3c.org>
Message-ID: <JIEGINCHMLABHJBIGKBCKEBIIGAA.julian.reschke@gmx.de>

> From: w3c-dist-auth-request@w3.org
> [mailto:w3c-dist-auth-request@w3.org]On Behalf Of Lisa Dusseault
> Sent: Saturday, September 06, 2003 12:17 AM
> To: 'Julian Reschke'; 'Nevermann, Dr., Peter'; w3c-dist-auth@w3c.org
> Subject: RE: getlastmodified of collections
> This is a good point.  I was thinking that the GET response to a directory
was likely only a
> listing of its member files, and then Geoff's idea of getlastmodified
would fit this model.


> However there are a number of other possibilities:
>  - If the server includes information about a directory's members, that
could change.  E.g.
> 	File Name		Size		Last Modified
> 	file1.txt		123k		8/1/2003
> 	file2.txt		124k		8/2/2003
>    A server that did a listing like this in response to a GET ought to
change its directory's
>    getlastmodified value whenever the content changed. Obviously that
might include a PUT
>    operation to a child as well as the other operations listed.


>  - If the server returns a file like "index.html" in response to a GET for
a directory, then
>    possibly the 'getlastmodified' property value for the directory should
be that of
>    the index.html file.


> How many HTTP/WebDAV clients are there out there that do caching/synch
based on the
> Last-Modified header or the 'getlastmodified' property?  I am guessing
there are quite
> a few because from what I've seen clients can't rely on ETag support in
Web/WebDAV servers.

I think most user agents will cache using the Last-Modified *header* when no
ETag is present. I however doubt that there are lots of WebDAV-aware clients
that actually use DAV:getlastmodified to cache (they'd still need to GET the
content, in which case they SHOULD use the "Last-Modified" header returned
by GET).

In general, all we can say reliably is that the Last-Modified date should
change when the GETtable content changes. Now the real issue here is: is the
timestamp allowed to change even though the content didn't. We ruled that
out for property changes (which I think is wrong), but seem to propose it
for other non-content changes here.

See also
part 2.

<green/>bytes GmbH -- http://www.greenbytes.de -- tel:+492512807760
Received on Saturday, 6 September 2003 05:46:43 UTC

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