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Re: [ontolog-forum] Logic, Datalog and SQL

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Ed Barkmeyer <edbark@xxxxxxxx>
Date: Thu, 08 Feb 2007 13:22:11 -0500
Message-id: <45CB6A53.70204@xxxxxxxx>
Adrian Walker wrote:    (01)

> Actually, if there is to be a new Wikipedia or other encyclopedia entry on
> logic for ontologies, it should summarize the ongoing debate between the
> "closed" and "open" world negationist camps.     (02)

I would welcome that, but I wonder how many rounds it will take to get a 
version that is acceptable to most of the parties involved.    (03)

It is my impression that there are at least 3 importantly different models of 
the "closed world", and they probably relate to what kind of inferences the 
"camp" wants to make.  Further, there are several problems that arise when the 
closed worlders need to mix "closed" concepts and "open" concepts.    (04)

One can, for certain "instantaneous" inferences, assume that the universe is 
finite and consists only of things recorded in the current information base. 
But to account for the evolution of that information base over time, one 
obviously cannot make that assumption.  And one has to step very carefully 
through the swamp that is created when these notions get mixed.  That is why, 
Michael Kifer, for example, says that all rules languages are programming 
languages.  They model a carefully chosen inferential procedure.    (05)

As to Adrian's examples:    (06)

> Almost all uses of databases
> in our everyday life rely on things like "if it's not in the catalog we
> don't stock it",     (07)

This is probably a business rule.  It is true because, like Jean-Luc Picard, 
we "make it so".    (08)

> "if no flight number to Podunk is in the database, then
> there is no flight to Podunk"     (09)

that we can do anything about.    (010)

The speaker doesn't actually care whether there is a flight to Podunk; he is 
focussing only on knowledge that affects HIS behavior.  But knowledge that 
does not affect his behavior might very well affect the behavior of some other 
person who has access to the same information.    (011)

> so we should not ignore closed world 
> usage of
> databases just because the clasical logicians never wrote about it.    (012)

I'm not a crazy evangelist for monotonicity, either.  I only point out that 
closed world systems are designed for a particular purpose, and in general, 
you cannot use them safely for inferencing for any other purpose.    (013)

-Ed    (014)

Edward J. Barkmeyer                        Email: edbark@xxxxxxxx
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263                Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263                FAX: +1 301-975-4694    (015)

"The opinions expressed above do not reflect consensus of NIST,
  and have not been reviewed by any Government authority."    (016)

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