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Re: Valid representations, canonical representations, and what the SW needs from the Web...

From: Stefan Eissing <stefan.eissing@greenbytes.de>
Date: Mon, 3 Feb 2003 12:01:28 +0100
Cc: <julian.reschke@gmx.de>, <www-tag@w3.org>
To: Patrick.Stickler@nokia.com
Message-Id: <D7F70763-3766-11D7-A23E-00039384827E@greenbytes.de>


Am Montag, 03.02.03, um 09:52 Uhr (Europe/Berlin) schrieb 
Patrick.Stickler@nokia.com:
>
>> -----Original Message-----
>> From: ext Julian Reschke [mailto:julian.reschke@gmx.de]
>> Sent: 02 February, 2003 23:00
>>>> [...]
>>>> What's not really possible right now is to have metadata for
>>>> a resource
>>>> (PROPFIND succeeds) with no representation (GET/HEAD fail),
>>>> because that's
>>>> not really compatible with the underlying model (PROPFIND for
>>>> non-collection
>>>> resources basically being an extended HEAD method with XML
>>>> marshalling).
>>>
>>> Well, if that's true, then WebDAV definitely fails as a solution
>>> to standardized access to resource metadata, since one would expect
>>> to be able to use the same solution for all resources, whether or
>>> not any representation is available.
>>>
>>> Pity...
>>
>> OK. So how do we expect HEAD to behave when no representation
>> is available?
>
> Well, as it appears that HEAD only returns metadata describing
> the representation, and not metadata describing the resource,
> then neither HEAD nor PROPFIND are acceptable solutions to this
> problem.
>
> It looks like we need something new. Such as a new set of methods,
> GET-META, PUT-META, POST-META, which would by definition deal with
> metadata describing the resource itself, and would also ideally
> by definition accept/return RDF.
>
> Patrick
>

WebDAV offers this and, yes, one could store RDF data in a single
or several properties as WebDAV properties can keep arbitrary XML.

What Julian mentioned is that one has to define what the result
of GET/HEAD on a "meta-only" resource would be. Maybe a 404
is approriate, maybe not. WebDAV has no answer to that currently
and I'm not sure what the correct behaviour should be. Maybe a
406 could also work.

But that issue needs to be solved by *any* out-of-GET-band
method which returns meta data for resources without representations.

//Stefan
Received on Monday, 3 February 2003 06:01:38 GMT

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