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RE: [topicmapmail] RDF and TopicMaps: an Exercise in Convergence

From: Daniel Rivers-Moore <Daniel.Rivers-Moore@rivcom.com>
Date: Fri, 1 Jun 2001 10:21:55 +0100
Message-ID: <E485423D7B760543AC1ABEA06BCD7B2E03860F@rivcom.rivcom.com>
To: <topicmapmail@infoloom.com>, <www-rdf-interest@w3.org>, "KnoW-Members" <KnoW-Members@rivcom.com>
[bernard vatant (on topicmapmail and rdf-interest lists)]
> The bottom question: Do you really consider that RDF Resource and TM
> Topic are equivalent (or isomorphic) concepts, in the sense that any
> information captured in an RDF Resource can be captured in an 
> equivalent way by a TM Topic (and the other way round) ? Or do you 
> consider it for the moment as a formal equivalence?

[sam hunting (on topicmapmail and rdf-interest lists)]
> This is a good question from Bernard that has not yet been answered.
> Humans are the ultimate arbiters of subject identity. If the same is
> NOT true in the RDF realm (can someone inform me?) then the
> homeomorphims between RDF and XTM is purely formal.

My version of this question is also my reply to Dan Brickley's question
to Paul Prueitt and the topicmapmail list, as follows:

[dan brickley (on topicmapmail list)]
> As an RDF-oriented Web developer, I'd be interested to hear some more
> details on the difference between RDF and Topic Maps. What precisely
> missing from RDF that makes it unappealing?

A key difficulty in making a mapping from RDF to Topic Maps is the lack
of clarity in RDF about what exactly is meant by the rdf:about and
rdf:resource attributes. The value of each of these attributes is a URI
string, and it is supposed to designate a "resource" that participates
in the triple. The question is whether this URI string is

1) A unique name for the thing that participates in the triple

2) A pointer to a file on some computer system whose content indicates
what the thing is that participates in the triple

3) A pointer to the actual thing that participates in the triple (in
which case only files on computer systems can participate in triples)

My experience with RDF would seem to indicate that the answer to this
question is not stable: it is sometimes used in each of these ways. If
we knew that just one of these was the correct usage, then we could make
a clear mapping between RDF and Topic Maps. Alternatively, we could
develop a mapping, and make it normative in order to provide an answer
to the above question. The vocabulary of Topic Maps allows us to be
precise about these subtle but vital distinctions, and the formalism of
Topic Maps allows us to give precise expression to them. The lack of
such distinctions in the RDF formalism is what limits its scope and
usability. However, if the scope were defined precisely (through a clear
answer to the above question, and/or a clear mapping to other formalisms
such as Topic Maps), then its usefulness would be greatly enhanced
because its meaning would become clearer.

For information, the KnoW initiative (Knowledge on the Web -
www.knowweb.org) is in the process of putting together a collaborative
project to study some of these questions, in relation not only to Topic
Maps and RDF but also a number of other specifications and technologies.
We hope to be able to contribute to the dialogue in helpful ways.

Kind regards

Daniel Rivers-Moore
Director of New Technologies, RivCom
Member of XML Topic Maps Authoring Group
Secretary of KnoW (Knowledge on the Web)

-----Original Message-----
From: Sam Hunting [mailto:sam_hunting@yahoo.com]
Sent: 31 May 2001 18:23
To: Bernard Vatant; Graham Moore; topicmapmail@infoloom.com;
Subject: Re: [topicmapmail] RDF and TopicMaps: an Exercise in

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Received on Friday, 1 June 2001 05:26:48 UTC

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