- From: Pat Hayes <phayes@ihmc.us>
- Date: Thu, 26 Jun 2008 15:57:54 -0500
- 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
- Message-Id: <p06230904c489af76cf65@[10.100.0.140]>
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 > > > > >_________________________________________________________________ >Message Archives: ><http://ontolog.cim3.net/forum/ontolog-forum/>http://ontolog.cim3.net/forum/ontolog-forum/ >Subscribe/Config: ><http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/>http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/ >Unsubscribe: ><mailto:ontolog-forum-leave@ontolog.cim3.net>mailto:ontolog-forum-leave@ontolog.cim3.net >Shared Files: <http://ontolog.cim3.net/file/>http://ontolog.cim3.net/file/ >Community Wiki: <http://ontolog.cim3.net/wiki/>http://ontolog.cim3.net/wiki/ >To Post: ><mailto:ontolog-forum@ontolog.cim3.net>mailto:ontolog-forum@ontolog.cim3.net > >=================================== > >P Please consider the environment before printing this e-mail > > > >Cleveland Clinic is ranked one of the top hospitals >in America by U.S. News & World Report (2007). >Visit us online at http://www.clevelandclinic.org for >a complete listing of our services, staff and >locations. > > >Confidentiality Note: This message is intended for use >only by the individual or entity to which it is addressed >and may contain information that is privileged, >confidential, and exempt from disclosure under applicable >law. 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Received on Thursday, 26 June 2008 20:58:36 UTC