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

["Adrian Walker" <adriandwalker@xxxxxxxxx>]

Hi Ed --

Actually, the thought was that since the closed/open world negation debate generates so much heat, an encyclopedia entry for logic and ontologies could shed some light on the matter by clearly setting out the arguments on both sides.  The entry would not need to resolve the issue, just clarify it.  Perhaps with examples about where each kind of negation works best.

You wrote...

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.

Actually, there appears to be a rather easy way out of the swamp, at least in principle and for some purposes:

  * Associate, with each chunk of information, a list of start times and end times.

  * Never delete any information, just grow the time lists, and add new "timed" information

  *  Associate with any answer to a question about the information, the time point(s), or time period(s), for which the answer is valid.

  *  When querying, use closed world negation at will.

Storage intensive, but perhaps worthwhile.  Or am I overlooking something?

                                         Cheers,  -- Adrian

Internet Business Logic (R)
A Wiki for Executable Open Vocabulary English
Online at www.reengineeringllc.com
                                Shared use is free
Adrian Walker
Reengineering
Phone: USA 860 830 2085

On 2/8/07, Ed Barkmeyer <edbark@xxxxxxxx> wrote:

Adrian Walker wrote:

> 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.

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.

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.

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.

As to Adrian's examples:

> 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",

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

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

that we can do anything about.

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.

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

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.

-Ed

--
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

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

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