[seek-kr] RE: Please tear this apart...

Shawn Bowers bowers at sdsc.edu
Mon Sep 8 11:24:57 PDT 2003


On Mon, 8 Sep 2003, Rich Williams wrote:

> Of course the units ontology I wrote is only a small piece of what you are
> asking about, but none the less, I think it is an ontology by most common
> computer science definitions and is quite similar to the units ontology that
> you posted.  (Of course this begs the question of what is the difference
> between an ontology and a database schema - in general, my answer is 'not
> much'...  See for example p156 in Sowa's Knowledge Representation book)
> 

I agree with you, computer scientists treat the term "ontology" as
synonymous to conceptual schema, like an E-R diagram or even an
OO schema (with classes and attributes). However, I think it is useful to
treat an ontology and a conceptual schema as two different beasts -- an
ontology serves to capture the domain model or theory: it is a 
description for understanding the assumptions and definitions of concepts
in a domain, and a conceptual schema is a particular representation for
the concepts.  

In my opinion, in SEEK we need to figure out whether we need a conceptual
schema, an ontology in the classic sense, or both.  It struck me in ABQ in
our KR breakout session, that we really need a clear articulation of the
way we use terminology, and the basic way we have chosen to model
ecological ideas (this is what I was trying to get at in the model I sent,
for measurements). We spent a lot of time in our session dealing with
basic terminology -- in fact, for part of the session people were actually
using the same terms to mean different things.  

For the idea of a "semantic type," an ontology in the classic sense is 
probably not what we want. The reason being, that a semantic type implies 
something is being typed (like a particular measurement, or a complex 
structure, like a list of measurements, etc.) 

I could see the ontology as sitting on top of the semantic-type 
conceptual schema. The ontology defines the theory behind the 
semantic-types, and the semantic-types allow us to capture and reason 
about the values flying around the pipeline, or coming from datasets. 
Reasoning may also involve the ontology as well, e.g., to help us 
understand the classification of things.  Users of SEEK (e.g., domain 
scientists) might enjoy using the ontology more than the conceptual 
schema, e.g., for querying or registering data sets. 

As a side note, I think some of the confusion of computer scientists
(including myself -- I obviously don't have a firm understanding of the
differences between ontologies and conceptual schemas as evidenced by my
emails) arrises from the particular language being used.  For example, RDF
is a language for representing semantic networks (a classic KR language, a
la Sowa), which can be used to define all sorts of things including
conceptual schemas.  Thus, to a computer scientist, everything described
in a semantic network is an ontology (in fact, I don't think computer
scientists really care if it is an ontology or a conceptual schema -- its
the processing/querying/storing that surrounds the language that is
important).


Shawn


> I've checked in a slightly revised version of it, and also a new figure that
> includes the slot relationships that hopefully makes its structure clearer
> (I omitted them in the original for clarity).  I also isolated my attempt at
> describing measurements from its extension to ecological measurements in
> particular and called the ontology MeasurementBase.  It's in the same
> seek/projects/kr/ontologies folder as the Units ontology.  It includes the
> units ontology, and so gives a picture of how units relate to measurements
> etc.  There's a figure, MeasurementBase.gif, of the ontology.
> 
> Rich
> 




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