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RE: subject indicators ... ?

From: Stella Dextre Clarke <sdclarke@lukehouse.demon.co.uk>
Date: Mon, 27 Sep 2004 10:46:40 +0100
To: "'Bernard Vatant'" <bernard.vatant@mondeca.com>, "'Miles, AJ \(Alistair\) '" <A.J.Miles@rl.ac.uk>, "'Charles McCathieNevile'" <charles@w3.org>
Cc: <public-esw-thes@w3.org>
Message-ID: <000701c4a476$e5bf6b40$0300000a@DELL>

Bernard,
Thanks for the explanation. It seems "subject indicator" is intended to
be more like "example" than like "definition", and I don't have a
problem with this. There may be a lag, however, before many producers of
thesauri think of taking up this facility. Few of them are likely to
have been following the conversations in the Semantic Web community. So
I guess some time may pass before the idea catches on for widely used
thesauri.
Stella

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Stella Dextre Clarke
Information Consultant
Luke House, West Hendred, Wantage, Oxon, OX12 8RR, UK
Tel: 01235-833-298
Fax: 01235-863-298
SDClarke@LukeHouse.demon.co.uk
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-----Original Message-----
From: Bernard Vatant [mailto:bernard.vatant@mondeca.com] 
Sent: 27 September 2004 07:50
To: Stella Dextre Clarke; 'Miles, AJ (Alistair) '; 'Charles
McCathieNevile'
Cc: public-esw-thes@w3.org
Subject: RE: subject indicators ... ?



Stella, Alistair, Charles, and all

> If I've understood correctly, the idea is to point (using a URL) to a 
> place where a definition of the concept appears.

Stella, you understood *almost* correctly :)

In fact, the creators of the notion of subject indicator were not as
ambitious and arrogant as to figure that subjects can always be
*defined* absolutely. Remind you that in the original context (topic
maps), a subject is *whatever can be talked about*, not only concepts in
structured concept schemes. Providing a proper and absolute definition
of a subject might often be difficult or even impossible, but a well
chosen resource can "indicate" by any means what the subject is about.
In a scheme containing color concepts, e.g. "Lavender Blue", the subject
indicator resource could be a sample of this color, along with its RVB
code.

> (And this is not the same as pointing to a place where an example 
> appears)

Well, for some subjects, a bunch of examples could be more efficient to
indicate the subject than a convoluted definition :)

> Rather than pointing to that
> other place, is it not better just to give the text of the definition?

All the point of subject indicators external to the scheme is to enable
identification of identical concepts in different schemes, whatever the
process this can trigger, like merging of topics in topic maps, which
was the primary intended use of subject indicators.

But actually, I figure that a subject indicator for a concept in scheme
A could be a concept in scheme B, itself providing a definition that A
doesn't care to reproduce. In fact I am curious to know what folks think
about the use of subject indicators vs scheme mapping.

> There could be an advantage if the text is too long or complex to 
> import; or if the aim is to allow the definition to vary according to 
> the dictat of the owner of the resource pointed to.

Well, certainly, using a subject indicator that you don't control is
some kind of risk, and means common trust. That's why was introduced the
notion of Published Subject Indicators, that should include all the
context necessary to support a trustable use of subject indicators.

For example http://antwrp.gsfc.nasa.gov/apod/astropix.html is a quite
good subject indicator for the subject "Astronomy Picture of the Day" :
"Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional
astronomer."

This resource is changing every day according to the declared dictat of
its owner ... but is in fact remarquably trustable. It's been there
since '95 and is one of the most stable changing resource I know of on
the Web ...

> For the sake of the integrity of the original scheme, it would seem 
> safer to be sure
what
> the concept is and not leave it to someone else's control! ( That way 
> you can be more confident of the relationships with other concepts in 
> the same scheme.)

Well, this has been debated over and over in various Semantic Web lists.
All the idea of the "Web of Trust" is indeed to have  resources
defining, and authorities publishing, concepts, and users using them in
full trust, the same way you trust the network when you send an email or
put an URL in your browser, and assume it will get to the right person
or retrieve the relevant resource. You have the same issue with the OWL
use of "import". When you import an external ontology in your own one,
you trust the imported source, either to be stable, or to change in a
way that will not screw up your own.

In fact, this is a fundamental choice in open environments, and
experience indeed shows that it does not work that bad. Even if you have
a breakdown of trust in 10% of cases (and this is very pessimistic, the
actual figure will certainly be lower), what you gain in the other 90%
is really worth it.

Cheers

Bernard

Bernard Vatant
Senior Consultant
Knowledge Engineering
Mondeca - www.mondeca.com
bernard.vatant@mondeca.com
Received on Monday, 27 September 2004 09:46:45 GMT

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