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Re: [OEP] Closed vs Open World $swbpd

From: Christopher Welty <welty@us.ibm.com>
Date: Fri, 17 Dec 2004 20:24:56 -0500
To: "Uschold, Michael F" <michael.f.uschold@boeing.com>
Cc: public-swbp-wg@w3.org, public-swbp-wg-request@w3.org
Message-ID: <OF079651C4.69AEFE3F-ON85256F6E.000795FC-85256F6E.0007C71D@us.ibm.com>
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.


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: 

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


[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, 
suggest when you want an open vs. closed world reasoner?
*                does the Semantic Web infrastructure offer any closed 
*                If not, then what do we say to a user who does not care 
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.


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Received on Saturday, 18 December 2004 01:25:29 UTC

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