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RE: Hierarchical URLs and Collections

From: Yaron Goland <yarong@microsoft.com>
Date: Tue, 18 Aug 1998 17:52:24 -0700
Message-ID: <3FF8121C9B6DD111812100805F31FC0D087923D7@RED-MSG-59>
To: "'Jim Davis'" <jdavis@parc.xerox.com>, WebDAV <w3c-dist-auth@w3.org>
Cc: Larry Masinter <masinter@parc.xerox.com>
I thought the reason references don't solve the problem is that in the cases
where all the security/scalability/consistency matters are resolved it still
isn't possible for a resource to declare "I am contained in the following


> -----Original Message-----
> From: Jim Davis [mailto:jdavis@parc.xerox.com]
> Sent: Tuesday, August 18, 1998 5:08 PM
> To: WebDAV
> Cc: Larry Masinter
> Subject: RE: Hierarchical URLs and Collections
> At 01:01 PM 8/18/98 PDT, Larry Masinter wrote:
> > [I suggest] that there
> >be a DAV:parents property and that interoperable clients ... use
> > PROPFIND of DAV:parents in order
> >to walk up the hierarchy, rather than just trying to parse the URL
> >tree. It's simple, backward compatible, doesn't cost much in terms of
> >server implementation, and much more resiliant.
> This proposal resembles some proposals that were discussed in 
> the context
> of so-called 'strong' references, and which were found 
> problematic then.
> 1) for the common case (internal membership) it adds no 
> value, because one
> can find the parent container by mere syntax.
> 2) for the uncommon case (referential membership), it's 
> problematic, because:
>  1. Security: When I create a referential resource whose 
> target is another
> resource I may not have the access to the target resource to 
> set the back
> pointer.  
>  2. Privacy: I may not want the target to know I am linking to it
>  3. Scalability: If the target is very very popular it won't scale.  
> Also, I don't see that it addresses the actual concerns 
> raised by the DMS
> community, as opposed to those that came up as side issues in the long
> discussion.  In my opinion, referential resources suffice to 
> completely and
> fully support such DMS systems.
> Furthermore, if it turns out that supporting such a property is a good
> idea, then I suggest the right thing is for the DMS vendor to 
> implement it,
> gain some experience, then propose it for a future version of 
> WebDAV.  In
> fact, we should look closely at the DMA API, which defines 
> two models of
> containment, Direct and Referential.  WebDAV has the former, and your
> proposal is like the latter.  To support Referential 
> containment requires
> general graph manipulation (as Y. Goland pointed out) and/or 
> transactions
> (which DMA has, sort-of).
> But anyway, unless someone can show why referential resources 
> do not solve
> the DMS vendor's problems fully, we should close this issue.  
> Jim
> ------------------------------------
> http://www.parc.xerox.com/jdavis/
> 650-812-4301
Received on Tuesday, 18 August 1998 20:52:07 UTC

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