|To:||"Adrian Walker" <adriandwalker@xxxxxxxxx>|
|Cc:||semanticweb@xxxxxxxxxxxxxxx, "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>, public-semweb-lifesci hcls <public-semweb-lifesci@xxxxxx>, semantic_web@xxxxxxxxxxxxxxxx, welty@xxxxxxxxxxxxxx|
|From:||Pat Hayes <phayes@xxxxxxx>|
|Date:||Wed, 25 Jun 2008 22:06:21 -0500|
At 8:37 PM -0400 6/25/08, Adrian Walker wrote:
Hi John --
Allow me to respond also.
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 .
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.
On Mon, Jun 23, 2008 at 10:54 PM, John F. Sowa <sowa@xxxxxxxxxxx> wrote:
40 South Alcaniz St.
_________________________________________________________________ Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/ Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/ Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx Shared Files: http://ontolog.cim3.net/file/ Community Wiki: http://ontolog.cim3.net/wiki/ To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx (01)
|<Prev in Thread]||Current Thread||[Next in Thread>|
|Previous by Date:||Re: [ontolog-forum] Fwd: Ontolog invited speaker session - Dr. Mark Greaves on the Halo Project - Thu 2008.06.19, Adrian Walker|
|Next by Date:|
|Previous by Thread:|
|Next by Thread:|
|Indexes:||[Date] [Thread] [Top] [All Lists]|