Hi Pat --
I hesitate to debate with such a distinguished logician as yourself.
However, what about SQL? Much of our commercial and scientific life depends on it, and it undoubtedly uses negation as "failure to prove".
Are you saying that we should move all commercial databases to a different query language using classical negation?
Cheers, -- Adrian
Internet Business Logic
A Wiki and SOA Endpoint for Executable Open Vocabulary English over SQL and RDF
Online at www.reengineeringllc.com Shared use is free
Adrian Walker
Reengineering
On Wed, Jun 25, 2008 at 11:06 PM, Pat Hayes < phayes@xxxxxxx> 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
[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 Shared use is free
Adrian Walker
Reengineering
On Mon, Jun 23, 2008 at 10:54 PM, John F.
Sowa <sowa@xxxxxxxxxxx>
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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