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Re: [ontolog-forum] owl2 and cycL/cycML

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
Cc: Bernardo Cuenca Grau <bcuencagrau@xxxxxxxxxxxxxx>
From: Ed Barkmeyer <edbark@xxxxxxxx>
Date: Mon, 02 Aug 2010 12:45:46 -0400
Message-id: <4C56F63A.9050602@xxxxxxxx>

Ian Horrocks wrote:    (01)

> Regarding my claim that reasoners are typically used in a way that is 
>actually incorrect, to the best of my knowledge none of the incomplete 
>reasoners in widespread use in the ontology world even distinguish "false" 
>from "don't know" -- whatever question you ask, they will return an answer. 
>Thus, in order to be correct, applications would have to treat *every* "false" 
>answer as "don't know". I don't know of any application that does that.
>       (02)

Put another way, it is not incorrect to treat "don't know" as "false", 
if "negation as failure" is a stated principle of the reasoning 
algorithm.  We can state the 'negation as failure' principle generally 
as "if the assertion cannot be proved from the knowledge base, the 
assertion is taken to be false."     (03)

Of course, "proved" means that the reasoning algorithm can derive a 
proof, which depends on the algorithm actually implemented in the 
engine.  As Ian mentioned earlier, this kind of "proof" implies that the 
nature of the reasoning algorithm is, or incorporates, "model 
construction", which is typical of various kinds of logic programming 
engines, but there are many hybrid algorithms.     (04)

-Ed    (05)

Edward J. Barkmeyer                        Email: edbark@xxxxxxxx
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263                Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263                FAX: +1 301-975-4694    (06)

"The opinions expressed above do not reflect consensus of NIST, 
 and have not been reviewed by any Government authority."    (07)

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