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RE: owl:Thing and RDF

From: Hans Teijgeler <hans.teijgeler@quicknet.nl>
Date: Thu, 27 Oct 2005 21:48:10 +0200
Message-Id: <200510271948.j9RJmBUI000796@vmx60.multikabel.net>
To: "'Frank Manola'" <fmanola@acm.org>, "Herman, Ivan" <ivan@w3.org>
Cc: <semantic-web@w3.org>
Hi Frank and Ivan,


Thank you for your responses!


Two opinions, and this poor newbie must make a choice, where he had hoped
for a solution:



Ivan Herman wrote:


I think that


- if you use OWL Full, then owl:Thing is equivalent to rdf:Resource, you
can't be more general than that:-)

- if you use OWL DL or Lite, than you *have* to use owl:Thing, this is the
way you identify individuals


Ie: the safe bet is to use owl:Thing. You do not loose anything and, if at
some point you have a smaller ontology that turns out DL or Lite, then you
are all set.


Just my personal opinion...




Frank Manola wrote:


Hi Hans--


I'm probably not the most reliable guide on OWL dialects, and I'm not sure I
fully understand what you're doing.  However, I don't see the need to use
owl:Thing explicitly at all.  My understanding is, if you create a
user-defined OWL class, e.g.,


<owl:Class rdf:ID="UserDefinedClass"/>


or as a triple


ex:UserDefinedClass rdf:type owl:Class  .


then UserDefinedClass is implicitly a subclass of owl:Thing;  you need not
say anything else.  Then, if you create an instance myInstance and type it
as a member of that OWL class, e.g.,


ex:myInstance rdf:type ex:UserDefinedClass  .


then myInstance is implicitly an instance of owl:Thing.  This is true in any
of the OWL dialects.





Since both seem OK to me, the question arises why this is possible at all.
Why has the SW been made so complex? Time for a clean-up?


Frank, if I would follow Ivan's advice, and typically use something explicit


    <owl:Thing rdf:ID="PHO-387392"/>

    <owl:Thing rdf:about="#PHO-387392">


        <rdfs:label>Joe Blogg</rdfs:label>



do you see any REAL disadvantage (other than the neglect of RDF)? Given the
fact that we use OWL very rigorously by superimposing the ISO 15926-2 data
model, clearly and consistently distinguishing individuals from classes by
using owl:Thing seems to fit in that rigor (or rigour, if you want). 


We have to work with IDs like PHO-387392 anyway, since we deal with more
than 20,000 classes and hundreds of thousands of individuals (all the things
that make up an entire oil refinery, and the components thereof, and the
process streams). We had a discussion about naming, and rejected
human-understandable names. What would be the human-understandable name for
a Ford Focus with a wide (not yet made) selection of engines, colors,
accessories, etc? And what if that selection has been made?





PS We have to use OWL Full. OWL DL simply is too restricted. But given the
fact that we have that superimposed data model in place, the reasoning isn't
that complex, nor important.


Hans Teijgeler

ISO 15926 specialist



phone +31-72-509 2005      
Received on Thursday, 27 October 2005 19:49:15 UTC

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