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Re: [Fwd: SIG2 Amsterdam meeting - summary]

From: Nicola Guarino <Nicola.Guarino@ladseb.pd.cnr.it>
Date: Tue, 8 Jan 2002 04:36:52 -0500 (EST)
To: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>, Mike Dean <mdean@daml.org>
Cc: Guido_Vetere@tivoli.com, www-archive@w3.org
Message-id: <a05100309b85f61e3d57d@[]>
At 1:19 AM +0100 19/12/01, Frank van Harmelen wrote:
>Mike (Cc Guido and Nicola),
>Below input from Guido Vetere on suggestions for the Web Ontology 
>language, as input for the January meeting of the Working Group.
>He raises some very interesting issues not raised by others before:
>- whether other relations then "subclassOf" (such as "partOf") 
>should be included in the language (he argues cogently why not).
>- He does argue to introduce some other distinctions, though. In 
>particular between "essential" and "non-essential" roles.
>(I believe this is closely connected to the remarks by Dan Brickley 
>on time-varying roles, in his recent message to the WebOnt group at 
>- the need for better supporting natural-language "names" for the 
>objects in the language than is currently available in RDF.
>(Guido, Nicola: Mike has taken over my role to collect input for the 
>meeting, which is why I forward your contribution to him).
>    ----
>-------- Original Message --------
>Subject: SIG2 Amsterdam meeting - summary
>Date: Tue, 11 Dec 2001 16:56:54 +0100
>From: Guido_Vetere@tivoli.com
>To: Frank.van.Harmelen@cs.vu.nl
>CC: Nicola.Guarino@ladseb.pd.cnr.it
>Hi Frank,
>here is a brief summary of my remarks on the SIG2 meeting, to be used as an
>input for the W3C ongoing discussions.
>1 - Modeling 'part' relations: formal vs substantial features (whether the
>ontology language should include the 'part' relation or not).
>In my opinion, although mereology is a very formal theory, 'part' is not a
>formal relation itself. In fact, its meaning depends on the 'particulars'
>it applies to: sortals, material entities in general, collections,
>space-time locations, and so on.  As a formal language, the W3C ontology
>syntax should avoid the introduction of such non-formal elements.

Hi Guido,

	sorry for this late feedback. I must say I disagree with this 
view: the part-of relation is in my opinion a "formal" relation, in 
the precise sense that it does not imply any constraints on its 
arguments: you can have parts of ideas, parts of objects, parts of 
events... In all these cases, I believe there is a common meaning of 
the notion of "part", which corresponds to a minimal set of axioms: 
part-of is intended as a partial order (asymmetric, antireflexive, 
transitive), plus the so-called "weak supplementation" axiom, which 
says that if x is a proper part of y then some z must exist, which is 
als a proper part of y but it is different from x. This corresponds 
to what Peter Simons says at the end of his seminal book "Parts - A 
study in ontology" (Clarendon Press 1987). I quote below a 
significant passage (p. 363):

"If this is all there essentially is to the part-of relation, why can 
stronger principles sometimes apply? The answer lies not in the 
part-relation itself but in the nature of the objects to which it 

An important case of a specialized part-of relation is the member-of relation:
a member of a collection is a special part of the collection, which 
exhibits a peculiar property: unity. This is why member-of is not 
transitive, while part-of is. Again, however, member-of is a formal 

Nicola Guarino
National Research Council       phone: +39 O49 8295751
LADSEB-CNR                      fax:   +39 O49 8295763
Corso Stati Uniti, 4		email: Nicola.Guarino@ladseb.pd.cnr.it
I-35127 Padova              

(***updated 19/12/2001 ***)
Received on Wednesday, 9 January 2002 17:05:18 UTC

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