Re: [OEP] Closed vs Open World $swbpd

Given that it is mentioned in all the OWL Rec documents, I don't think it 
needs its own note, however I think this clearly goes in the "pitfalls" 
document, which is on our list for next year.

-Chris

Dr. Christopher A. Welty, Knowledge Structures Group
IBM Watson Research Center, 19 Skyline Dr., Hawthorne, NY  10532     USA   
 
Voice: +1 914.784.7055,  IBM T/L: 863.7055, Fax: +1 914.784.7455
Email: welty@watson.ibm.com, Web: 
http://www.research.ibm.com/people/w/welty/



"Uschold, Michael F" <michael.f.uschold@boeing.com> 
Sent by: public-swbp-wg-request@w3.org
12/17/2004 06:58 PM

To
<public-swbp-wg@w3.org>
cc

Subject
[OEP] Closed vs Open World   $swbpd







We just encountered the time-honored 'problem' of what happens when a
user assumes/expects closed-world inference, and gets open world.

Unless two classes A and B are provably disjoint (possibly via an
explicit disjoint axiom), a DL reasoner will not conclude that A is in
the complement of B.

This can be seen as a feature, because it allows you distinguish between
"can't prove it" and "can prove that it is false".

It could also be experienced as a problem (read: big pain in the neck)
by a user who does not need to make that distinction, because it forces
them to add bunches of disjoint axioms.

This is a likely source of confusion for some users. 
It would be good if we could say something about this. Questions that
users may wish to be discussed/answered include:

*                are there any identifiable characteristics of a domain, 
which
suggest when you want an open vs. closed world reasoner?
*                does the Semantic Web infrastructure offer any closed 
world
reasoners? 
*                If not, then what do we say to a user who does not care 
to
distinguish not provable from provably not and finds it a nuisance to
add all those disjoint axioms? They are unlikely view as helpful, a
comment such as: "You should be glad to be forced to model your domain
more carefully".

I think that we should try and say something about this somewhere, it is
bound to come up over and over.
Is there a note that this topic might be covered in?
Should we have separate, short not on it?
Does anyone have enough expertise/experience to say something sensible
on the topic?

Alan Rector may know more about this than anyone, with all the users
encoding bio ontologies in DLs.

Mike


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