[Top] [All Lists]

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

To: "John F. Sowa" <sowa@xxxxxxxxxxx>
Cc: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Thu, 8 Feb 2007 17:12:12 -0600
Message-id: <p06230925c1f15ab04c02@[]>
>I completely support Pat's discussion of closed worlds
>and open worlds.  This is not a "debate", but a discussion
>of how to handle two kinds of databases, both of which
>are important for various applications:
>   1. Open worlds, such as information derived from
>      observation, in which the absence of an entry
>      does not imply its negation.
>   2. Closed worlds, such as information derived from
>      an exhaustive enumeration or a declaration by fiat;
>      i.e., anyone whose reservation has not been entered
>      in the database does not have a reservation.
>Both kinds arise in many applications, and both must
>be supported.  I also agree with Pat that the term
>"negation as failure" is misleading and that "negation
>by inference" is a better term.
>Once you adopt that term, you can begin to ask what
>kinds of inferences should be supported.  Failure
>to prove (or observe) is a common basis for the
>inference, but there can be more subtle variations.
>For example, the fact that I haven't observed an
>elephant in my living room allows me to infer with
>high probability that no elephant is lurking there.
>But my failure to observe any bacteria in the living
>room does not imply their absence.    (01)

Right. There is a fascinating line of research, 
BTW, on inferences which people make intuitively, 
seem to be surprisingly reliable, and seem to 
have the general form "If x were y, I would know 
about it; I havn't heard of x; therefore x isn't 
y" This enables for example German students to 
make reliable guesses about which American cities 
are larger than others. I first heard of this in 
the work of Gerd Gigerenzer on 'bounded 
rationality'. See 
http://en.wikipedia.org/wiki/Recognition_heuristic    (02)

What I find fascinating is that this seems to 
depend on there being just the right amount of 
generally available public information, a lot but 
not all of it. It wouldn't have worked in a 
medieval society and it might not work in the 
future for the opposite reason: people will all 
know too much.    (03)

>Having thrown in this bit of support, I'd like to make
>a brief comment on our argument about models and reality:
>   1. Pat prefers to identify the model with the thing
>      that is modeled, except in circumstances when the
>      thing modeled may not exist or may be difficult
>      to observe in sufficient detail.    (04)

That isn't how I would put it myself :-)    (05)

>   2. I prefer to make a distinction between the two in
>      all cases, but allow the option of saying that they
>      may sometimes be identical or at least isomorphic.    (06)

I will agree that an interpretation need not 
*always* be made up of real stuff, as it were. In 
fact it is easy to show that this is false: if an 
ontology has any satisfying interpretations at 
all, then it has a Herbrand interpretation 
entirely made of symbols. My only point was that 
it is *possible* to interpret ontologies directly 
against the actual world (and this is often a 
useful thing to do, if only as part of a thought 
experiment.)    (07)

>This reduces the debate to a question of relative importance
>or frequency.
>But there is one important reason for making the distinction
>between the model and the thing modeled:  it allows the
>possibility of discussing and comparing different models and
>deciding which one(s) have a better correspondence with
>reality.    (08)

Oh, sure. But here you are using "model" in what 
I called the model-2 sense, right, rather than 
the Tarskian sense used in "model theory". Then 
this becomes the Korzybskian slogan that the map 
is not the territory: which is true, of course.    (09)

Pat    (010)

>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
>    (011)

IHMC            (850)434 8903 or (650)494 3973   home
40 South Alcaniz St.    (850)202 4416   office
Pensacola                       (850)202 4440   fax
FL 32502                        (850)291 0667    cell
phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes    (012)

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    (013)

<Prev in Thread] Current Thread [Next in Thread>