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Re: [OEP] Purpose of the note on "classes as values". [Was: Close to final draft of "classes as values" note]

From: Natasha Noy <noy@SMI.Stanford.EDU>
Date: Thu, 13 May 2004 17:42:07 -0700
Message-Id: <86DDE83C-A53F-11D8-93C6-000A958B5C28@smi.stanford.edu>
Cc: "swbp" <public-swbp-wg@w3.org>
To: Bernard Vatant <bernard.vatant@mondeca.com>, Brian McBride <brian.mcbride@hp.com>

All (and Bernard and Brian in particular),

[Nothing like putting "close to final" on the subject line to catch 
people's attention :) ]

I think I still failed to articulate what the goal of the "classes as 
values" note is (or at least what I saw as the goal when I was drafting 

It is NOT about how to link thesauri and ontologies in general or in 
particular. It is NOT about how to link your new ontology to a legacy 
vocabulary or your new vocabulary to a legacy ontology.

What I was trying to do, was answer the question that comes up all the 
time: I am developing an ontology, and the most natural way to 
represent what I want is to reference classes from this hierarchy X in 
instances of these other classes. The moment I do this, I am in OWL 
Full. If I'd rather stay in OWL DL, what are my options? Indeed, this 
question comes up in the context of annotating individuals from your 
ontology with classes from some "legacy" hierarchy, but not only there.

If someone who sees the difference here could try and re-write the 
preamble so that this point is clear, I would really appreciate that 
(seriously, we need to make the difference clear, and I don't seem to 
be able to articulate)!

So, to address Brian's concerns (I'm taking his points somewhat out of 
order, but it's easier this way):

> Approach 1 is described as being in Owl Full.  I looks to me like RDFS 
> until
> the extension to restrict the values of dc:subject is introduced.  That
> restriction doesn't seem to be about the main purpose of the note, i.e.
> about defining subject hierarchies.  I suggest it might be useful to
> separate out the RDFS solution and that Owl FULL solution, with 
> separate
> examples of each.

This comment makes sense if you view the note as a description of how 
to link thesauri with individuals in an ontology. With the caveat 
above, does it still stand? (It seems that whether or not it is RDFS is 
beyond the point, given the goal)

> I also note that the example seems very close to the work of the 
> thesaurus
> task force.  I'm a bit nervous about this overlap.

Do you still see this as overlap given the point above? And why would 
you be nervous about that anyway?

> Has it been reviewed by the DC folks?

To the best of my knowledge, no. Again, the goal here is NOT to discuss 
proper uses of dc:subject. I've asked this question (and the trade-off 
of using dc:subject or some local made-up property) here:


There was never any reply, but I am still wondering if it's worth using 
something other than dc:subject (the natural question of "why didn't 
you use dc:subject" notwithstanding)

Similarly, to Bernard:

> First I would like to see more precise definition of the use cases in 
> each approach : what
> is given (the legacy), what are the objectives of the use case, and 
> what is to be built to
> achieve them.
> Basically we have two KOS : on one side an ontology, on the other side 
> a
> classification-indexing system (a library system, to make it short).
> It's unclear in each approach if the use case is :
> #1 : Both ontology and library system are considered as given in the 
> legacy, have been
> built and managed independently, and the problem is to map them, from 
> one side or another.
> The use case should make it clear which is the master and which is the 
> slave.
> #2 : The two systems are developed together in an integrated 
> environment. This looks like
> a "closed" use case not really in the scope of the Semantic Web 
> deployment. Maybe we
> should skip that one.
> #3 : One of the system is built to be best interoperable with the 
> other, which is given
> (can be both ways).

Either one of them. It is true that in some of the approaches we make 
some changes on the ontology side and in some on the vocabulary side, 
but I really wasn't thinking in those terms. Again, the goal was 
somewhat different. (And certainly it's not #1, since most of the 
approaches assume that you have control over either one or the other).

Again, you may not have two different systems at all. Somewhere in your 
ontology you may have a hierarchy that you need to reference from 
somewhere else and staying in OWL DL is your concern (or not).

Subjects are used only as an example.

I'll reply to other points in a separate email.

Received on Thursday, 13 May 2004 20:44:26 UTC

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