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Re: LANG?/SEM?: using resources (was Re: LANG: owl:ontology)

From: Christopher Welty <welty@us.ibm.com>
Date: Wed, 18 Sep 2002 12:07:07 -0400
To: www-webont-wg@w3.org
Message-ID: <OF0AB81F58.ACF39F54-ON85256C38.0057A7C4@pok.ibm.com>

Let me try to clarify my case hopefully using something closer to y'all's 
hearts.  I realize most of the people in this group are not strictly 
ontology researchers, so I'll use a KR language example:

Someone comes along and sees the OWL spec.  "Oh," they say, "I like this 
SameClassAs thing, it's transitive.  I just need something transitive, I 
don't need the rest of this OWL monster."  So they build a system that 
uses the OWL:SameClassAs tag, and they use it in cases like this:

Car OWL:SameClassAs Engine
Engine OWL:SameClassAs SparkPlug

The fact is that OWL:sameClassAs does not mean Part.  If you borrow this 
tag and use it FOR SOMETHING ELSE, then you shouldn't be using this tag. 
If you don't agree with the full semantics of OWL:sameClassAs, then don't 
borrow that tag.  Create one of your own.

The same goes for borrowing symbols from ontologies.  If you don't want to 
commit to the full semantics or meaning of a symbol as specified in some 
ontology, then don't borrow it from that ontology.  Make up your own, this 
tells everyone that you may mean something different.  Borrowing the 
symbol from the ontology should tell people that you intend the same 
thing.

-Chris






Christopher Welty/Watson/IBM@IBMUS
Sent by: www-webont-wg-request@w3.org
09/18/2002 11:47 AM

 
        To:     www-webont-wg@w3.org
        cc: 
        Subject:        Re: LANG?/SEM?: using resources (was Re: LANG: owl:ontology)

 


I'm not sure I'm following you at all here.  Let's see if this makes 
sense:

The "definition" of a resource or symbol is not identifiable in a 
syntactic way - it is the "meaning" of the symbol in my ontology.  The 
best I can do in a symbolic system is to constrain the way that symbol can 

be related to others, this helps me and other users "narrow down" the 
potential misunderstandings.  These constraints are in my ontology.  So, 
to enforce that my definition is adhered to, you must use my entire 
ontology.

Look, if someone wants to build an ontology that claims to use Chris' 
notion of what "car" means, then they must be constrained to use it in the 

way I said.  That HAS TO BE what referring to an external symbol means - 
it has to give us a way to come to a shared understanding.    It's not a 
convenience or a shortcut for people who don't want to write axioms.

If you are just looking to reuse a few symbols and axioms that someone 
else wrote, then cut and paste them into your ontology.  If you don't want 

to COMMIT to all the constraints I put on the symbols in my ontology, then 

YOU ARE NOT USING MY SYMBOL, so don't refer to it.  Copy the part you want 

to reuse and call it something different.

If you build an ontology that uses Chris' defintion of Car, and someone 
else comes along and sees it and says, "Oh, my system is compatable with 
Chris' defintition of car, he is such an expert on that, I trust his 
definition.  So I can use this ontology, too."  If you allow someone to 
arbitrarily "borrow" just the symbol from my ontology, then it is easy for 

someone to claim they are using my defintion of car, but to allow things 
like motorcycles be included under that defintion, and thus violate the 
meaning of "chris's definition of car".  We have lost everything.

-Chris







"Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Sent by: www-webont-wg-request@w3.org
09/18/2002 10:40 AM

 
        To:     Christopher Welty/Watson/IBM@IBMUS
        cc:     www-webont-wg@w3.org
        Subject:        LANG?/SEM?: using resources (was Re: LANG: 
owl:ontology)

 


As far as I can see, there are several ``strange attractors'' in this
space:

Attractor 1:  Resources have definitions.

Attractor 2:  Whenever a resource is used, the intent of the ``definer'' 
of
  that symbol is automatically a consequence of that use, whether that
  intent is in the form of a definition or even in some other form.

These two seem to be attractive at first glance, but have untenable
consequences in both the RDF and OWL world view.

Attractor 1 has a technical problem.  There is no reasonable way in RDF to
separate out the triples that could form the definition of a symbol, even
if one might argue that the symbol has a definition.  Similarly, OWL has 
no
notion of what would make up the definition of a class, a property, or an
individual.  I don't see any tenable way of adding the notion of a
definition to OWL, particularly OWL written in RDF.

Because resources can't have definitions in RDF or OWL, Attractor 2 can't
use the notion of a resource.  However, even if there was a way of
selecting the definition of a resource, automatically having the
definition of a resource being a consequence of the use of the resource is
a bad idea.

For example, suppose I want to be able to mention the Taliban in an OWL
ontology.  I have to pick a well-known resource that is commonly used to
refer to the Taliban.  If Attractor 2 is in force, as soon as I do so, I 
am
committed to whatever the definition of that resource is.  In the case of
the Taliban, I would be forced to choose among the various definitions of
the Taliban, most of which would force rather strong consequences.  The
situation would be even worse if I wanted to related the various
definitions, as I would end up with a contradition just by making a
co-reference between the various definition.

The situation is even worse with Attractor 2 in the absence of
definitions.   To get the intent of the definer of the resource, I would
have to commit to an entire document (or ontology, if you prefer).  Here I
would end up with things like committing to the invasion of Iraq just by
mentioning George W. Bush.


As far as I can see the only viable route is to be able to use resources
without committing to anything related to that resource.  To commit to
something in some other ontology/document, use imports.


Peter F. Patel-Schneider
Bell Labs Research
Received on Wednesday, 18 September 2002 12:07:44 GMT

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