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RE: Versioning, Collections and Sources

From: Slein, Judith A <JSlein@crt.xerox.com>
Date: Thu, 17 Dec 1998 17:49:52 -0500
Message-ID: <201BB34B3A73D1118C1F00805F1582E8B76D38@x-wb-0128-nt8.wrc.xerox.com>
To: "'Yaron Goland'" <yarong@microsoft.com>, "'Greg Stein'" <gstein@lyra.org>, w3c-dist-auth@w3.org

> -----Original Message-----
> From: Yaron Goland [mailto:yarong@microsoft.com]
> Sent: Wednesday, December 16, 1998 5:13 PM
> To: 'Greg Stein'; w3c-dist-auth@w3.org
> Subject: Versioning, Collections and Sources
> 

> The collection folks may want to consider a
> source like model where you have paired resources. The "redirection"
> resource and its "control". The "redirection" resource will 
> respond to one
> magic method which returns a header which specifies the 
> "control" resource.
> The "control" resource is then the one that arbitrary methods 
> can be applied
> to.   This solution is VERY far from optimal since servers will have
problems
> managing the parallel namespaces and dealing with potential name
conflicts.

Let's see if I'm understanding your suggestion: Every reference has 2 URIs,
one of which can be used to operate on the target and one of which can be
used to operate on the reference.  If you do a PROPFIND on a collection, you
get the URI that operates on the target.  If you want to operate on the
reference, you send some new method, say GETREFURI, which returns the URI
that operates on the reference.  Then you send your request to that URI.
(Both of these URIs are different from the value of DAV:reftarget, which is
a URI that locates the target resource via a collection where it is an
internal member.)

I have no strong objection to this implementation.  Compared to the
No-Passthrough header, it results in one additional round trip for the case
where you want to operate on the reference, but this case is probably by far
less common than operating on the target.  I don't really see that it's such
a big deal for the server to provide a second identifier for the reference.
It would be selected by the server, so it's not as if the client provides a
name that might collide with some other name.  If others share your concern
about coming too close to URL-munging with the No-Passthrough header, we
could certainly make this change.

So if you want to get the content of the target of a *direct* reference,
here's the sequence of messages:

1. PROPFIND /collection1/
2. Response includes /collection1/reference1, showing properties of the
target
3. GET /collection1/reference1
4. Response is the content of the target resource

But if you want to update the properties of the *direct* reference itself,
you do:

1. PROPFIND /collection1/
2. Response includes /collection1/reference1, showing properties of the
target
3. GETREFURI /collection1/reference1
4. Response includes the URI for operating on the reference: /collection1/r1
5. PROPPATCH /collection1/r1
6. OK, properties of reference were updated

If you want to get the content of the target of a *redirect* reference, you
do:

1. PROPFIND /collection1/
2. response includes an entry for /collection1/reference1, with a 302
response code and a location element that contains DAV:reftarget
3. GET on DAV:reftarget
4. Response is the content of the target resource

But if you want to update the properties of the *redirect* reference itself,
you do:

1. PROPFIND /collection1/
2. Response includes an entry for /collection1/reference1, with a 302
response code and a location element that contains DAV:reftarget
3. GETREFURI /collection1/reference1
4. Response includes the URI for operating on the reference: /collection1/r1
5. PROPPATCH /collection1/r1
6. OK, properties of reference were updated

--Judy

Judith A. Slein
Xerox Corporation
jslein@crt.xerox.com
(716)422-5169
800 Phillips Road 105/50C
Webster, NY 14580
Received on Thursday, 17 December 1998 17:44:59 GMT

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