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Re: Modeling a specific construct - please help

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 16 Sep 2009 15:10:56 -0500
Cc: Alan Rector <rector@cs.man.ac.uk>, Uli Sattler <sattler@cs.man.ac.uk>, Milan Zdravkovic <milan.zdravkovic@gmail.com>, public-owl-dev@w3.org
Message-Id: <ADA764AD-634C-4B50-9654-4E4BA3BDC86D@ihmc.us>
To: Chimezie Ogbuji <chimezie@gmail.com>

On Sep 16, 2009, at 9:50 AM, Chimezie Ogbuji wrote:

> On Tue, Sep 15, 2009 at 4:24 AM, Alan Rector <rector@cs.man.ac.uk>  
> wrote:
>> Well, no, you cannot (validly) conclude this. This is a non-monotonic
>> inference, which is not supported by the OWL semantics. While it  
>> may work in
>> particular cases where you know that your data is complete in the  
>> required
>> sense, it is not good practice to use such inference patterns in  
>> OWL, as
>> they will (not may, but WILL) break in some cases. Think building a  
>> glass
>> building over a known seismic fault.
>>
>> Pat Hayes
>
>> The difficulty with such reasoning patterns is that they only work  
>> when you
>> can
>> complete the knowledge base so that it is fully constrained.
>> In most of our biomedical models, we can rarely be certain enough
>> that all possibilities have been covered to reason that the only
>> possibilities left over are true, only that they might be and may
>> ]be worth further investigation.
>
> True, but I've found (in practice) that non-monotonic reasoning
> matches well with the intuition behind clinical medicine and the way
> electronic patient data can be recorded as RDF (mostly using strict
> data entry controls where it is important to assume at least a portion
> of the data is complete in order to make reasonable inferences from
> it)

Well, let me rephrase my point somewhat differently. If you use this  
inference pattern, and come to rely on it, and then in some case you  
find it delivers false conclusions, do not complain to anyone about  
RDF or OWL, or complain to the proprietors of the RDF or OWL reasoner  
you are using. Do not say that your reasoner is broken. Go instead to  
whoever gave you the data you were using and upon whose completeness  
you were relying, to serve the writs, or voice the complaints, or  
whatever.

Pat

>
>> Although we have sometimes used this kind of reasoning on very  
>> restricted
>> data entry problems with multiple constraints where we can be sure  
>> that they
>> can all be covered.  In those cases the non-monotonicity is an  
>> advantage,
>> although I would try to confine it to increasingly large queries  
>> rather than
>> the KB itself. As we learn more, we add it to the query, so that  
>> query gets
>> larger and the number of
>> possible answers to the remaining questions gets fewer.
>> This sort of reasoning used to be supported in the Protege Query  
>> tab, but is
>> no longer.
>> Regards
>> Alan
>
> -- Chimezie
>

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Received on Wednesday, 16 September 2009 20:12:53 GMT

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