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Re: [ontolog-forum] Fwd: Ontolog invited speaker session - Dr. Mark Greaves on the Halo Project - Thu 2008.06.19

From: Chimezie Ogbuji <ogbujic@ccf.org>
Date: Thu, 26 Jun 2008 16:05:20 -0400
To: "Pat Hayes" <phayes@ihmc.us>, "Adrian Walker" <adriandwalker@gmail.com>
cc: "[ontolog-forum]" <ontolog-forum@ontolog.cim3.net>, "John F. Sowa" <sowa@bestweb.net>, welty@watson.ibm.com, semantic_web@googlegroups.com, "public-semweb-lifesci hcls" <public-semweb-lifesci@w3.org>, semanticweb@yahoogroups.com
Message-ID: <C4896EC0.325D%ogbujic@ccf.org>
Just a quick comment.  Pat H. wrote

[[
The basic snag with negation as failure is that it is almost always not
valid. It is simply wrong. The cases where you can validly infer, from a
failure to prove P, that P is false, are extremely rare. They only occur in
specialized circumstances in specialized tasks performed by specialists in
certain limited cases.
]]

I would disagree about this case being the exception.  Negation as failure
can be validly used to infer from a failure if the data is controlled (which
is especially the case with well-designed experiments where it would be
irresponsible to to do otherwise).  If a clearly-defined protocol is used as
part of the data collection process (for example, only assert P if P is
known), then you can make valid inferences about missing content without the
burden of classic negation, which requires a significant amount of effort
(either having a large amounts of assertions about class disjointedness,
etc. or requiring explicit assertions about the absence of data) to ensure
that you can prove  that P is false.

On 6/25/08 11:06 PM, "Pat Hayes" <phayes@ihmc.us> wrote:

> At 8:37 PM -0400 6/25/08, Adrian Walker wrote:
>> Hi John --
> 
> Allow me to respond also.
> 
>> You wrote...
>> 
>> It's important for us to develop Common Logic as the growth path
>> for ontologies and to incorporate CL in the Semantic MediaWiki.
>> 
>> Anything currently represented in either the Semantic Web notations
>> or relational databases can be mapped to Common Logic.  And the
>> more compact CL notation is vastly more efficient in storage space,
>> transmission time, and computation time than the current Semantic
>> Web notations.
>> 
>> We should position CL as the foundation for Semantic Web 3.0.
>> 
>> You may like therefore to address Chris Welty's point that CL appears
>> infeasible for the W3C rule interchange project.  In slide 11 of [1], Chris
>> says:
>> 
>> The CL and IKL approach [is] deprecated: infeasible for this group [W3C Rule
>> Interchange], as major differences appeared irreconcilable (e.g. non-mon vs.
>> mon)
> 
> He is there referring to a particular approach, viz. to adopt a highly
> expressive language into which all rule languages can be translated, which was
> used in the IKRIS project which produced IKL. If however you read on in the
> same slides, you will find that the language finally adopted as the initial
> Rule standard, though much weaker than CL, in fact is a classical logic with a
> classical negation, just like negation in every other logic with a clear
> semantics.
> 
>> The fundamental difficulty seems to be
> 
> That isnt the fundamental difficulty for RIF.
> 
>> that CL and IKL have chosen a theoretical semantics for negation
> 
> Its not especially 'theoretical'. It is simply what negation means in ordinary
> language. If you say cows are white, and I say, No, cows are brown; then my
> "no" says that what you said is false. That simply is what negation means.
> This is a common-sense, pre-theoretical notion of negation. So-called
> 'negation as failure' is the theoretical notion, and it only arises from
> database theory. The basic snag with negation as failure is that it is almost
> always not valid. It is simply wrong. The cases where you can validly infer,
> from a failure to prove P, that P is false, are extremely rare. They only
> occur in specialized circumstances in specialized tasks performed by
> specialists in certain limited cases. Can you prove that every finite abelian
> group can be expressed as the direct sum of cyclic subgroups of prime-power
> order? Answer quickly. Suppose, just for the sake of argument, that you can't.
> Are you justified in concluding that this is false? Maybe you had better hedge
> your bets.
> 
>> from before the computer era, whereas SQL and most logic based programming
>> languages use a different meaning for negation -- one that can also be
>> formalized, e.g. as in [2].
> 
> It can be formalized, for sure. It can in fact be formalized in many
> different, incompatible, ways. All of them however make it vividly clear that
> this is not a generally correct inference rule.
> 
> Pat
> 
>> 
>> Thanks for your thought about this.
>> 
>>                                        -- Adrian
>> [1]  
>> http://ontolog.cim3.net/file/resource/presentation/ChrisWelty_20080612/W3C-Ru
>> les-Interchange-Format--ChrisWelty_20080612.ppt
>> <http://ontolog.cim3.net/file/resource/presentation/ChrisWelty_20080612/W3C-R
>> ules-Interchange-Format--ChrisWelty_20080612.ppt>
>> 
>> [2]  Backchain Iteration: Towards a Practical Inference Method that is Simple
>>   Enough to be Proved Terminating, Sound and Complete. Journal of Automated
>> Reasoning, 11:1-22
>> 
>> Internet Business Logic
>> A Wiki and SOA Endpoint for Executable Open Vocabulary English over SQL and
>> RDF
>> Online at www.reengineeringllc.com <http://www.reengineeringllc.com>
>> Shared use is free
>> 
>> Adrian Walker
>> Reengineering
>> 
>> 
>> 
>> 
>>> On Mon, Jun 23, 2008 at 10:54 PM, John F. Sowa <sowa@bestweb.net> wrote:
>>>> 
>>>>> Peter,
>>>>> 
>>>>> Thanks for posting the audio for Mark Greaves talk.  I wasn't
>>>>> able to log in for the talk, but I read the slides.  The audio
>>>>> covers some important points that are not in the slides:
>>>>> 
>>>>> http://ontolog.cim3.net/cgi-bin/wiki.pl?ConferenceCall_2008_06_19
>>>>>> The Semantic MediaWiki is very important work, and since it is
>>>>>> available as open source, we should use it.
>>>>>> 
>>>>>> But one important point that Mark mentioned is that the reasoning
>>>>>> capabilities of current Semantic Web technology is very weak.
>>>>>> RDF(S), OWL, SPARQL, and RuleML are useful, but weak subsets
>>>>>> of Common Logic.
>>>>>> 
>>>>>> It's important for us to develop Common Logic as the growth path
>>>>>> for ontologies and to incorporate CL in the Semantic MediaWiki.
>>>>>> 
>>>>>> Anything currently represented in either the Semantic Web notations
>>>>>> or relational databases can be mapped to Common Logic.  And the
>>>>>> more compact CL notation is vastly more efficient in storage space,
>>>>>> transmission time, and computation time than the current Semantic
>>>>>> Web notations.
>>>>>> 
>>>>>> We should position CL as the foundation for Semantic Web 3.0.
>>>>>> 
>>>>>> John
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> _________________________________________________________________
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>>>>>> To Post: mailto:ontolog-forum@ontolog.cim3.net
>>>>>> 


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Received on Thursday, 26 June 2008 20:06:23 GMT

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