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Re: silly question about rdf:about

From: Lars Marius Garshol <larsga@garshol.priv.no>
Date: 15 Apr 2002 00:21:57 +0200
To: www-rdf-interest@w3.org
Message-ID: <m37kn9or96.fsf@pc36.avidiaasen.online.no>

* Uche Ogbuji
| 
| The straw man is that RDF uses http://uche.ogbuji.net to represent
| the person "Uche Ogbuji".  All the discussion about "published
| subjects", and odd tricks with unambiguousProperty seem to be
| solutions to this supposed problem.

They are solutions to the problem of how to establish the identity of
resources that are not network-retrievable, yes. RDF doesn't have a
solution for that at the moment, as far as I know, although a lot of
people seem to be groping for different ways of handling it.
 
| But I don't see why anyone thinks that RDF says
| http://uche.ogbuji.net *is* the person.  I also don't see what is
| special about a published subject identifier that makes it an
| acceptable stand-in for the person.

You mean a published subject *indicator*. There is nothing special
about the indicator, it's just that using it as an indicator does in
fact solve this problem. The idea is dead simple, but it works.

Let's say that we'd like anyone to be able to make statements about
the person "Steve Pepper" in such a way that their statements are
mergeable, even without direct communication between them.

What we do (did, in fact) is to publish a resource that identifies
"Steve Pepper", say <URL: http://psi.ontopia.net/ontopia/#4 >. Now
anyone who creates topics and give them this resource as a subject
indicator will find that their topics *do* in fact merge correctly.

There's an added benefit in that there is human-readable documentation
of what they meant their topics to represent, but that's just a
side-effect, really.

(Please ignore the fact that the document I referred to gives a
different URI as the identifier. We're still figuring out how best to
use this.)

The key point here is that you use a network-retrievable resource to
identify something that is not network-retrievable. You don't need to
invent a new URI scheme or anything, you just make it clear that
you're addressing not an existing resource, but something described
*in* that resource.
 
| If enough people agree that urn:folks:uche.ogbuji.net is an
| acceptable published subject identifer for "Uche Ogbuji", then they
| have already done all the work RDF needs to take advantage of this
| in description of the person.

If you can make a URI that addresses you directly, and that everyone
agrees addresses you, then you don't need a subject indicator, I
agree. This is the same in RDF and topic maps.

The good thing about topic maps is that it lets us use 

  <URL: http://uche.ogbuji.net >

as a subject indicator for you, without anyone confusing the web site
with the person. 

We know which topic represents you (the one that has this resource as
its subject indicator), and which one that represents the web page
(the one that has it as its subject constitutor). Note that a topic is
not a URI, but that it can have URIs in its "subject indicator" or
"subject constitutor" properties.

Did this help?
 
| I don't see that Topic Maps gains anything with this built-in
| indirection, 

It gives us a model anyone can understand for creating global
identifiers for things which are not network-retrievable. It avoids
the "bad practice trap" that RDF seems to have fallen into. It makes
it instantly clear which symbols represent network-retrievable things
and which ones don't.

As far as I know RDF doesn't have any of these things yet.

| except one of the most complex data models I have ever seen for a
| description language (puts CIM to shame, I must say).

Huh? What do you mean? What is the complexity?
 
| This is *not* a flame on Topic Maps.  TM has things that RDF
| desperately needs, such as scopes and merging, but I don't think
| that the subject/occurrence (or whatever) distinction is one of the
| things RDF needs.

Why not?

-- 
Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
ISO SC34/WG3, OASIS GeoLang TC        <URL: http://www.garshol.priv.no >
Received on Sunday, 14 April 2002 18:22:14 GMT

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