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From: pepke@gw.scri.fsu.edu (Eric Pepke)
Newsgroups: comp.object
Subject: Re: Combining AI and OOP ?
Message-ID: <244@sun13.scri.fsu.edu>
Date: 12 Jul 90 16:13:10 GMT
Sender: news@sun13.scri.fsu.edu
Organization: Florida State University, but I don't speak for them
Lines: 45
References:<1990Jul5.175904.810@urz.unibas.ch> <1947@runxtsa.runx.oz.au>

In article <1947@runxtsa.runx.oz.au> timm@runxtsa.runx.oz.au (Tim Menzies) 
writes:
> but what about default knowledge? surely thats a useful KR trick that 
needs
> a hierarchy of inheriting objects? not so says brachman. with defaults 
comes
> the ability to override defaults. the ability to override defaults 
effectively
> negates any knowledge representation power. if john is-a bachelor and 
john
> can override any or all of the properties of bachelor, then all you can 
say
> about john is that at sometime in the past, john had all the properies 
of a
> bachelor. since then, john could have done anything with his 
bachelor-ness.
> if defaults can be over-ridden, then you can 'tbe sure about any of 
john's
> properties right now.

I don't see any real problem with this.  I have a bicycle.  Bicycles have 
two wheels.  This is one of the most basic properties of bicycles and is 
the one from which it derives its name.  Let's say I forget to lock it up 
with the chain, only the U-lock, and somebody steals the front wheel.  
Would smoke come out of my ears if I were to say, "I have a bicycle, but 
it's front wheel is missing."?  Would it be unreasonable to say or think, 
"I need a new front wheel for my bicycle" rather than "I need a new front 
wheel for my that-which-is-not-a-bicycle but which, upon addition of a new 
front wheel, shall become a bicycle."?

Would it not make more sense to be able to look at the default that is 
overridden, see that it is a fundimental property of a bicycle, and be 
able to conclude thereby that there is something wrong with the bicycle?

I don't know whether objects are the best way to represent knowledge, but
to conclude that they are useless on the basis of such reductio ad absurdum
arguments is silly.

Eric Pepke                                    INTERNET: pepke@gw.scri.fsu.edu
Supercomputer Computations Research Institute MFENET:   pepke@fsu
Florida State University                      SPAN:     scri::pepke
Tallahassee, FL 32306-4052                    BITNET:   pepke@fsu

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