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Re: URI for language identifiers

From: Jan Algermissen <algermissen@acm.org>
Date: Wed, 02 Apr 2003 09:45:48 +0200
Message-ID: <3E8A952C.1D2F8158@acm.org>
To: Patrick.Stickler@nokia.com
CC: www-rdf-interest@w3.org

Patrick.Stickler@nokia.com wrote:

> 
> But if the URI denotes two things, how do you differentiate
> between statements made about one versus the other?

The URI does not denote two things. There are just two kinds of properties
on topics that use URIs as values. The semantics of the properties are
different.

The whole thing is different because in topic maps, you have an unlimited
number of possibilities to identify what a given topic represents.

> It comes down to whether there is one web or many. Most folks
> want there to be one web, not e.g. a REST Web and a Semantic
> Web. In order for the Semantic Web to be "part of" the one
> web, we need to be able to refer to anything whatsoever using
> URIs, and that includes abstract concepts and other non-web
> accessible resources.
> 
> Now some, including TimBL, would prefer to make a key distinction
> between URIs and URIrefs, where URIs only denote web-accessible
> resources, and URIrefs must be used to denote non-web accessible
> resources. Others, including myself, see no need for such a
> distinction.

This is helpful information to me, thanks.
 
> > >
> > > As far as RDF is concerned, one need never dereference any
> > URI and never
> > > get any representation. URIs denote resources and one may use RDF to
> > > make statements about resources. Representations are
> > entirely outside
> > > the scope of RDF proper.
> > >
> > > However, where RDF and the web architecture agree is on the
> > fundamental
> > > principle that URIs should have globally, consistent,
> > unambiguous, and
> > > immutable meaning.
> >
> > But you don;t need URIs for that, nor do you need the Web.
> > Maybe that is
> > what I don;t understand: what is the idea of how RDF
> > interacts/intermingels
> > with Web architecture (beyond the idea of 'controled vocabulary') ?
> 
> Well, fair enough. If you want your TMs to remain disjunct from the
> web, then fine, but there is then no point to this discussion. 

The point is (for me) to understand the mind of RDF, the ideas that
underly certain design decisions and you are helping me a lot.

> Since
> RDF is intended to operate effectively within the Web architecture
> it may simply not be useful to compare RDF and TMs.

Well, maybe. But to me it's enlightening ;-)

> 
> So, even though XTM may use URIs, it is perhaps not using them the same
> way as the rest of the world (web) and thus there is no basis whatsoever
> for interoperability between XTM and RDF.

Well, if RDF allows me to 'find out' what kind of thing are URI denotes
(web page vs. car) then I may be able to make use of that information in
topic maps.


> [..] But of course, one must have some
> idea of what some URI denotes before one can make statements about the
> resource denoted.
> 
> The key is knowing what it denotes, and that the denotation is consistent.

So, how do I find out what it denotes?

> > The denotation is not ambigous but there are two *ways to use* of URIs
> 
> If a single URI can denote both a web resource and an abstract subject,
> then it is ambiguous. Period. 

A URI allways denotes the 'web page'. Period. ;-)

> If the interpretation of a give URI depends
> on context, then it is ambiguous. Period. 

The context is explicit, so what is ambigous about that?

> XTM has ambiguous use of URIs.

No. Period. ;-)

> 
> > > And I say XTM, not TM, because this dichotomy is an XTM
> > invention not
> > > present in the original TM model.
> >
> > That is not true, the use of addresses (not only URIs) as
> > addresses for
> > information resources *and* as identifiers for subjects is at the core
> > of topic maps.
> 
> I don't read the ISO spec that way. I think that XTM reads alot into the ISO spec.

Well, this is not the place to qote the specs etc., trust me that I am right. The
relationship 'old ISO 13250' and XTM is about the same as SGML and XML.
 
> > > XTM first did the right thing by
> > > adopting URIs, and then broke everything by not preserving globally
> > > consistent, unambiguous, and immutable denotation.
> >
> > Hmm, what exactly do TMs brake?
> 
> I said XTM, not TMs. And if it's not clear from what I've said thus far,
> I see little point in saying it in yet another way.

Well, thanks anyway.

Jan


> 
> Patrick

-- 
Jan Algermissen                           http://www.topicmapping.com
Consultant & Programmer	                  http://www.gooseworks.org
Received on Wednesday, 2 April 2003 02:43:37 GMT

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