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Re: Some advice on inferring negated properties

From: Mark Montgomery <markm@kyield.com>
Date: Thu, 16 Aug 2007 15:30:24 -0700
Message-ID: <012801c7e055$0b7f1bb0$6500a8c0@Inspiron>
To: <public-owl-dev@w3.org>, "Pat Hayes" <phayes@ihmc.us>

Well, it's good to see that a sense of humor! It's easy enough to get 
cynical for those of us over 40ish (++ in my case) in this line of work, 
especially for anyone still wishing upon a star that machine to machine 
automation can be functional and flexible over time without regular 
(constant?) human intervention. And I am a big productivity fan. That said, 
I found the exchange between Tim and Bijan to be among the most beneficial 
in recent times from a practical vendor's perspective. We do need standards 
for the exchange of information, but we also need the possibility for 
functional work arounds, and incentives for everyone to engage- without 
which not much would have ever left the lab.

.02

Mark Montgomery
Kyield
Initium

----- Original Message ----- 
From: "Pat Hayes" <phayes@ihmc.us>
To: <public-owl-dev@w3.org>
Sent: Thursday, August 16, 2007 1:47 PM
Subject: Re: Some advice on inferring negated properties


>
>>On Aug 16, 2007, at 8:28 PM, Swanson, Tim wrote:
>>
>>>Bijan,
>>>
>>>Thanks again. I think you're right, the misunderstanding goes back to
>>>talking at cross-purposes. I have just one more question.
>>>
>>>>>(Admittedly, this is not the same thing as "directly" checking for
>>>>the
>>>>>negative entailment, since it relies on the user's understanding of
>>>>>OWL
>>>>>semantics to make the jump from membership in the above class to the
>>>>>negative entailment.)
>>>>
>>>>It's not a negative entailment (which for me means a *failure* to
>>>>entail) but an entailment of a negation, but yes. For Matt's purpose
>>>>this might be fine. OWL 1.1 statement entailment shall be added to
>>>>Pellet in due course (esp to support SPARQL). One could, of course,
>>>>write such a wrapper.
>>>>
>>>
>>>"negative entailment" = "failure to entail" (i.e. still unknown in the
>>>open world)
>>
>>More typically known as "non-entailment" (e.g., non-subsumption as well).
>>
>>I've never specifically heard "negative entailment" before, so I see I 
>>read it as a variant of "non-entailment".
>>
>>>"entailment of a negation" = "entailing that something is untrue" (i.e.
>>>known to be false)
>>
>>Well, the *negation* is true (entailed), but of course the negated 
>>sentence is false.
>>
>>>Is this the accepted language? (If so, I need to re-write some of our
>>>in-house documents to comply with it.)
>>
>>I feel that the above is standard.
>
> Right. Please, everyone: don't get not-entailed confused with 
> entailed-not.
>
> B is entailed by A when, if A is true then B has to be true.
>
> The negation of B, not-B, is true when B is false, and vice versa.
> So not-B is entailed by A when, if A is true then B has to be false.
>
> This leaves open the further possibility (which is overwhelmingly more 
> likely) that when A is true, nothing whatever follows about the truth or 
> falsity of B. Then neither of B nor not-B are entailed by A.
>
> (failure to entail B =/= B is unknown, since the first, but not the 
> second, allows for the possibility that not-B is entailed. Unknown is 
> failure to entail B and failure to entail not-B.)
>
> love to all
>
> Pat
>
>>
>>Cheers,
>>Bijan.
>
>
> -- 
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Received on Thursday, 16 August 2007 22:31:21 UTC

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