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Re: [OEP] Lists of Values

From: Natasha Noy <noy@SMI.Stanford.EDU>
Date: Wed, 19 May 2004 19:18:10 -0700
Message-Id: <F0CFB20E-AA03-11D8-A8F8-000A958B5C28@smi.stanford.edu>
Cc: best-practice <public-swbp-wg@w3.org>
To: Alan Rector <rector@cs.man.ac.uk>

[OEP task force name added to the subject]

Alan,

I have to qualify the rest of the comments with a disclaimer, that 
unlike for Alan, my preference lies with the second approach. That 
said, the note is so well done that Alan almost managed to convince me 
that the two approaches are equally good and I can easily see why (the 
issue of reasoners aside) the first approach can be preferable in some 
cases

I really like the note -- it outlines the choices clearly and gives a 
good explanation of what each choice entails.

I do have a few comments (of course! :)

I think the choice of height as an example is somewhat unfortunate: 
many readers would have in their mind that height is a quantity rather 
than a qualitative value and this may muddy the example for them 
somewhat (in particular for has_height property). I am not advocating 
changing the example, since it's a considerable hassle but thought I'd 
throw it out anyway. (Perhaps, something like personality -- introvert 
vs extrovert -- would have been a slightly better example.) At the very 
least, in the first paragraph for Approach 1, you may want to point out 
that there may also be a numeric property for height and that there is 
no relation between the two.

You may want to give a more detailed explanation of why approach 1 can 
be used for multiple partitioning and approach 2 cannot (a very 
important point). I had to spend some time to convince myself that this 
is the case and in fact I am not sure yet I am convinced. Perhaps an 
example of how you would do it in 1 and some explanation of why the 
same trick won't work for 2 would be sufficient.

In considerations for approach 1, I wasn't sure what second bullet 
meant.

To me having to create an instance of johns_height would  -- an extra 
level of abstraction that you don't have in approach 2 -- is at least a 
consideration (that makes 1 slightly more complicated)

In the OWL code for approach 2, you may want to put a comment next to 
the first "owl:differentFrom" statement that that's where you make all 
the instances different and without this statement, reasoning won't 
give the results expected.

In considerations for approach 2, I would be a bit more clear on bullet 
2 (really, the crucial one), Indeed, DL reasoners today cannot reason 
with individuals, but the correct expected reasoning is well within 
semantics that DL reasoners should be able to do. This is different 
from some other things in OWL DL (notably annotation properties, or 
approach 3 in "classes as values") where while we are still within OWL 
Dl, the reasoning that we might want to have is not really "DL 
reasoning" and we can't expect even future more complete DL reasoners 
to do that. So, the bullet may something like:

- Although the representation is in OWL DL and a DL reasoner can be 
expected to make correct inferences with individuals defined in this 
way, neither FaCT nor Racer (essentially the only two OWL DL reasoners 
that exist today) can do that inference now.

Bullet 2 in semantic/ontological issues has an incomplete sentence.

Natasha
Received on Wednesday, 19 May 2004 22:31:34 UTC

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