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

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 26 Jun 2008 15:57:54 -0500
Message-Id: <p06230904c489af76cf65@[10.100.0.140]>
To: "Chimezie Ogbuji" <ogbujic@ccf.org>
Cc: "Adrian Walker" <adriandwalker@gmail.com>, "[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
At 4:05 PM -0400 6/26/08, Chimezie Ogbuji wrote:
>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).

What are you referring to by "well-designed experiments"?

>  If a clearly-defined protocol is used as part of the data 
>collection process (for example, only assert P if P is known)

OK, but that does not ensure that if P is not asserted, then it is 
known to be false. In fact, rather the opposite.

>, then you can make valid inferences about missing content

You can make such inferences validly only when you have some reason 
to suppose that if the proposition were true, the content would not 
be missing. I don't mean to deny that such circumstances do exist, in 
some cases with an explicit warrant for the entailment, but they are 
certainly not the usual case. The usual case is that your knowledge 
is incomplete. Our knowledge of almost everything is incomplete.

>without the burden of classic negation, which requires a significant 
>amount of effort

Nonsense. There is no 'burden' of classical negation. Negation IS 
classical negation. If you conclude that P is false, and express this 
using a negation connective, you are using classical negation. (If 
your *conclusion* from a failure to prove P is that P is not proven, 
then your reasoning is completely classical also; but then you are 
only concluding failure, not negation from failure.)

>(either having a large amounts of assertions about class 
>disjointedness, etc. or requiring explicit assertions about the 
>absence of data)

You have to say what is true in order to draw reliable conclusions 
from it. This can be done in tedious ways or, with the right 
notations and conventions, more compactly. You are reacting against 
some of the more tedious notational results of using simple textbook 
logics. But if you want to be able to infer, from the fact that 
something is in a class A, that it is not in another class B, then 
you must have some way to know that A and B are disjoint. Because if 
they aren't, that conclusion is not valid. No amount of grumbling 
about classical negation is going to get over that basic fact. If you 
want to seriously propose that we should adopt as a logical principle 
that all classes with different names are disjoint, then tell me how 
you will discuss subclass relationships.

>to ensure that you can prove  that P is false.

You have to know somehow. You might just know because someone told 
you, or because you know that if it were true then you would have it 
recorded, and you don't. But you have to know this. You can't just 
guess it or hope that it will be true, and call the result a 'logic'.

Pat

>
>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-Rules-Interchange-Format--ChrisWelty_20080612.ppt>http://ontolog.cim3.net/file/resource/presentation/ChrisWelty_20080612/W3C-Rules-Interchange-Format--ChrisWelty_20080612.ppt 
><http://ontolog.cim3.net/file/resource/presentation/ChrisWelty_20080612/W3C-Rules-Interchange-Format--ChrisWelty_20080612.ppt><http://ontolog.cim3.net/file/resource/presentation/ChrisWelty_20080612/W3C-Rules-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><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>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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Received on Thursday, 26 June 2008 20:58:36 GMT

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