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Re: comment on URI and resource ownership in WebArch document

From: Dan Connolly <connolly@w3.org>
Date: Thu, 12 Feb 2004 11:50:44 -0600
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: public-webarch-comments@w3.org, Bijan Parsia <bparsia@isr.umd.edu>
Message-Id: <1076608243.29438.232.camel@dirk>

On Thu, 2004-02-12 at 11:32, Peter F. Patel-Schneider wrote:
> Comments on 
> 	Architecture of the World Wide Web, First Edition
> 	W3C Working Draft 9 December 2003
> 	http://www.w3.org/TR/2003/WD-webarch-20031209/
> The comments below address only one substantive, fundamental issue in the
> document.  I have other issues with the document (for example,
> authoritativeness of metadata) but these are all subsidiary to this one issue.
> I actually generally like the idea of having this sort of document.  It is
> a very good idea to delimit some of the principles of the World Wide Web.

Likewise, thanks for the careful review...

> (In fact, a similar document for the Semantic Web would also be very useful
> - perhaps one that abided by the third architectural basis of the World
> Wide Web.)
> The major issue that I have with the contents of this document concerns the
> related notions of ownership and authoritativeness.  I find that the
> document neither adequately defines nor uses these fundamental notions and
> that this problem undermines much of what the document is trying to do.
> The document defines a resource as an ``item of interest''.  This is a very
> broad definition, which includes things like 
> 1/ the Oaxaca Weather Report from WeatherExample,
> 2/ the Oaxaca weather report, i.e., some idealized representation of the
>    Oaxaca weather, and
> 3/ the Oaxaca weather.
> The document also uses URIs, as they are normally defined.  
> The document then talks about resource owners and URI owners.  However,
> unfortunately neither resource owner nor URI owner is well defined in many
> situations.

I'm quite sympathetic to this concern, but I just looked at the text
of the document the other day, and I'm pretty happy with the way it's

2.2. URI Ownership
The requirement for URIs to be unambiguous demands that different agents
do not assign the same URI to different resources. URI scheme
specifications assure this using a variety of techniques, including:

      * Hierarchical delegation of authority. This approach, exemplified
        by the "http" and "mailto" schemes, allows the assignment of a
        part of URI space to one party, reassignment of a piece of that
        space to another, and so forth.
      * Random numbers. The generation of a fairly large random number,
        used in the "uuid" scheme, reduces the risk of ambiguity to a
        calculated small risk.
      * Checksums. The generation of a URI as a checksum based on a data
        object has similar properties to the random number approach.
        This is the approach taken by the "md5" scheme.
      * Combination of approaches. The "mid" and "cid" schemes combine
        some of the above approaches.
The approach taken for the "http" URI scheme follows the pattern whereby
the Internet community delegates authority, via the IANA URI scheme
registry [IANASchemes] and the DNS, over a set of URIs with a common
prefix to one particular owner. One consequence of this approach is the
Web's heavy reliance on the central DNS registry.

Whatever the techniques used, except for the checksum case, the agent
has a unique relationship with the URI, called URI ownership. The phrase
"authority responsible for a URI" is synonymous with "URI owner" in this

The webarch doc doesn't say, for example, that for each URI there's
exactly one human being who has final say on what it means.

Is it the choice of the term "ownership" that concerns you most?
Could you help me understand what it is about the text that concerns
you most?

> Some URIs, notably many URIs in the http URI scheme, have authority
> components, which can be used to define a notion of ownership.  However,
> even for such URIs, the authority is often not the owner.  (For example,
> dl.kr.org is probably assigned to MIT, but doing a get on http://dl.kr.org/
> does not return a page that is owned by MIT.  In fact, the true owner of
> this page is Carsen Lutz.

Carsen Lutz does not have complete carte blanch to write anything on
that page, does s/he? The webarch text above makes it reasonably
clear, to me, that the "ownership" of this URI is held by some
combination of Carsen Lutz acting on behalf of some part of MIT.

>   This situation is actually quite common, where
> the owner of an html document is best determined by looking for the
> ``maintained by'' text.)  Many other URIs (e.g.,
> http://weather.example.com, xxx:yyy) simply do not have any authority or
> owner.
> Even if a URI has an owner, this owner does not, in general, ``enable the
> URI owner to serve authoritative representations of a resource.''
> Certainly there is no way that the owner of
> http://weather.example.com/oaxaca, if there was one, is in any special
> relationship to the Oaxaca weather or even the Oaxaca weather report, as
> this owner is not also the owner (or creator or controller or ...) of the
> Oaxaca weather or even the Oaxaca weather report.

I don't think we're saying they have control over the weather...
But in this example scenario, they do control the weather report.
I don't think I understand your concern.

>   (Well, I suppose that it
> might be possible for some owner to actually control the Oaxaca weather,
> but this is highly unlikely.)
> Even for resources that are created as documents on the World Wide Web, it
> is not necessarily the case that the owner of a URI that identifies a
> resource that is a Web document also owned by this owner will necessarily
> serve authoritative representations of this document.  There are many cases
> where better information about a Web document is available from other
> sources.  (Consider the caches maintained by Google, leaked versions of
> documents that are only available in censored form from their owner,
> documents that are only available in summary form but which can be
> reconstructed by others.)
> Given all these problems I don't see how the architectural principles of
> the World Wide Web can be so dependent on resource ownership.  Many of the
> uses of ``resource owner'' in the document do not make sense at all and
> need to be removed from the document.
> Peter F. Patel-Schneider
> Bell Labs Research
Dan Connolly, W3C http://www.w3.org/People/Connolly/
see you at the W3C Tech Plenary in Cannes 1-5 Mar 2003?
Received on Thursday, 12 February 2004 12:50:27 EST

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