Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!netnews.upenn.edu!msuinfo!sticklen
From: sticklen@cps.msu.edu (Jon Sticklen)
Newsgroups: comp.ai
Subject: Re: Survey:  how do  we really use objects?
Message-ID: <1990Dec1.210905.11102@msuinfo.cl.msu.edu>
Date: 1 Dec 90 21:09:05 GMT
References: <2588@runxtsa.runx.oz.au>
Sender: news@msuinfo.cl.msu.edu
Organization: Michigan State University
Lines: 36

From article <2588@runxtsa.runx.oz.au>, by timm@runxtsa.runx.oz.au (Tim Menzies):


I think the issues that Tim raises are very good ones. If you take the
issue as he posed it (What good are inheritance hierarchies in terms
of direct representation of expert knowledge?), then I think he is
correct that the (purely representational) hierarchies will become
very complex.

For example, if I tried to build a system for medical diagnosis around
the represetational idea of hierarchies, then I would have a very
complex structure in which some objects were diseases, some objects
were signs and symptoms, some were lab tests, and ... Moreover the
relationships between all these different types of nodes would let me
to a very tangled structure indeed.

But what is missing here is a decomposition of the overal problem
solving in some meaningful way such that all of these "hierarchies"
will be untangled. The job of diagnosis in a clinical setting 
has deeply embedded hierarchies of disease such that most clinical
practioneers will readily recognize them. 

These disease specialization hierarchies can be used to perform a type
of classificaiton problem solving. Other types of problem solving
necessary to drive the diagnosis (like inferences leading from known
data value to another, e.g., temp=105 => high fever) will not be
represneted in the hierarchy of diseases, but in a seperated knowledge
structure. 

The point here is that expert knowledge may well be hard to organize
if you use a syntax level representation tool like "object hierarchy".
On the other hand, if you have in your repetoire epistemic level tools
of analysis (like hierarchical classificaiton), then expert level
knowledge may be easier to represent in some semi-direct fashion.

	---jon---


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