Hi Ian, (01)
I beg to differ. Since it seems you are thinking only in academic terms,
you are missing the reality of how facts and rules are used by agents such
as people. The facts and rules provide the basis over which theorem-proving
algorithms work. The proof algorithms themselves are so well understood
that they have become common everyday words among academics. But the value
of these algorithms alone is so low that very few nonacademics are finding
them useful. (02)
If you "delegated the task of checking the facts to a stupid/careless
person" then it is quite likely that the facts and rules s/he asserted were
in error. S/he can prove any theory by adjusting the evidence to fit it.
So if "they told [us] that they weren't able to draw the conclusion", then
the entire project is flawed, and there are little truthfully useful results
to come out of it. The purpose of our work on this list should be on how to
make the -uctions useful to humans, not just to machines. (03)
In the legal and financial world, where people use deduction, induction, and
all the other tools of logic in a realistic world setting, the term "due
diligence" is used to indicate that the fact seeker spent an "appropriate"
amount of resources in discovering the facts, validating and verifying the
evidence. Any legal discovery case can literally go on forever, but the
judge will identify when all reasonable discovery issues have been
illuminated for both plaintiff and defense. Discovery stops then, not when
every fact has been placed into the puzzle of -uctions. MOST OFTEN, there
are facts FOR and facts AGAINST any conclusion. That is because people use
very subjective judgment, and are swayed by their own mental focus,
including their own best interests. You can consider them "stupid/careless"
people, but that would include all of us if the effects of self-interest are
looked at. We misjudge the facts all the time because we want a specific
outcome. (04)
In highly significant real world cases, such as the JFK assassination
beloved by reporters and conspiracy theorists, people are still "discovering
facts" they say are relevant, even though the official case has been closed
for over forty years. (05)
The point is, when a "stupid/careless person" gets facts and rules wrong,
s/he can prove or disprove anything at all. The point is to balance
reasonableness of discovery with the most objectively reviewed evidence, and
no more - Occam again. It's not which deduction algorithm that is so
important - it's the factual basis and the rule accuracy that have to be
dealt with now that deduction methods are so well understood in the academic
community. (06)
That is why web sites still sell evidentiary content and not reasoning for
the most part. Blogs and other opinion sites sell a specific reasoning
story, but have little sway with the public - they're more entertaining than
truthful. (07)
-Rich (08)
Sincerely,
Rich Cooper
EnglishLogicKernel.com
Rich AT EnglishLogicKernel DOT com
9 4 9 \ 5 2 5 - 5 7 1 2 (09)
-----Original Message-----
From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Ian Horrocks
Sent: Monday, August 02, 2010 11:11 AM
To: [ontolog-forum]
Subject: Re: [ontolog-forum] owl2 and cycL/cycML (010)
Sorry, but you are missing the point. (011)
The point is that a given conclusion *can* be proven with the facts at our
disposal, it's just that we delegated the task of checking the facts to a
stupid/careless person, and they told as that they weren't able to draw the
conclusion. (012)
Please let's not muddy the waters with this discussion of NAF -- it is
really a red herring. (013)
Ian (014)
On 2 Aug 2010, at 18:54, Rich Cooper wrote: (015)
> Hi Ian,
>
> If the intent of the tool's designers is to mimic human perspectives on
> knowledge and logic, then negation as failure is more human like, IMHO,
than
> any existing alternative. A person with no experience in an area normally
> is very skeptical of assertions that can't be proven within his/her
database
> of factual and structural knowledge, and reaches the same conclusion. I'm
> sure you've heard it said that you don't know what you don't know, so you
> assume you know everything until proven otherwise.
>
> Another way to look at it is that, within the bounds of evidence, a judge
or
> juror has no basis for any conclusion that is not consistent with known,
> demonstrated facts. It is always possible that other information will
> surface in the future, but the rational deduction of the present moment
has
> to be based on known facts, not on missing information.
>
> One consequence of this result is that it is very hard to convince anyone
of
> a fact which has no familiarity, in specific or general terms, to them
> personally. That is why attorneys and laws depend on known facts.
>
> -Rich
>
> Sincerely,
> Rich Cooper
> EnglishLogicKernel.com
> Rich AT EnglishLogicKernel DOT com
> 9 4 9 \ 5 2 5 - 5 7 1 2
>
> -----Original Message-----
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Ian Horrocks
> Sent: Monday, August 02, 2010 10:14 AM
> To: edbark@xxxxxxxx; [ontolog-forum]
> Cc: Bernardo Cuenca Grau
> Subject: Re: [ontolog-forum] owl2 and cycL/cycML
>
> It is even more tricky that this. The failure in "negation as failure"
> doesn't mean failure of a given algorithm, it means not provably true.
There
> are many decidable logics with NAF. If we have an incomplete reasoner for
> such a logic, we are *still* incorrect if we take failure to return "True"
> as being equivalent to "False", because the failure may simply be a
symptom
> of the incompleteness and nothing to do with NAF.
>
> Simple example: I am using a logic in which negation is interpreted as
NAF.
> I have a simple boolean theory in which negation isn't used and which
> entails A(x). I ask if A(x) is entailed. My incomplete (for entailment)
> reasoner answers "False". If I treat this as entailing that A(x) is not
> entailed, then I am really incorrect -- nothing to do with NAF.
>
> In fact I think that we would be well advised to strike NAF from the
record
> -- it's really not helpful in this discussion :-)
>
> Ian
>
>
>
>
>
> On 2 Aug 2010, at 17:45, Ed Barkmeyer wrote:
>
>>
>> Ian Horrocks wrote:
>>
>>> 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.
>>>
>>
>> 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."
>>
>> 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.
>>
>> -Ed
>>
>> --
>> 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
>>
>> "The opinions expressed above do not reflect consensus of NIST,
>> and have not been reviewed by any Government authority."
>>
>>
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