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RE: owl:Thing and RDF

From: Benjamin Nowack <bnowack@appmosphere.com>
Date: Sun, 30 Oct 2005 12:45:51 +0200
To: "Hans Teijgeler" <hans.teijgeler@quicknet.nl>
Cc: <semantic-web@w3.org>
Message-ID: <PM-EH.20051030124551.7C25.1.1D@192.168.27.2>

On 30.10.2005 09:57:02, Hans Teijgeler wrote:
>Would this be acceptable:
>
><owl:Thing rdf:ID="PHO-387392">
>
>       <rdf:type
>rdf:resource="http://www.iso15926.org/part2/2003-12#PhysicalObject"/>
>
></owl:Thing> 
>
>?
>PS    Then it is close to what the military do: name, rank and number. The
>number of resulting triples seems to be the same as Frank's:
>
><iso:PhysicalObject rdf:ID="PHO-387392"/>

Using "owl:Thing" will lead to an additional

 #PHO-387392 rdf:type owl:Thing

triple. If you don't do any reasoning based on the explicit "owl:Thing"
typing, you may also just use

<rdf:Description rdf:ID="PHO-387392">
   <rdf:type rdf:resource="...#PhysicalObject" />
</rdf:Description>

instead, which will result in a single triple only, "rdf:Description"
is a syntactical construct that won't show up when the rdf/xml is 
parsed to plain triples.

benjamin

--
Benjamin Nowack

Kruppstr. 100
45145 Essen, Germany
http://www.bnode.org/

>
> 
>
>The "Thing" solution may have an advantage for me in that for individuals
>that exist in space-time we have more than one typing to do, e.g.:
>
><owl:Thing rdf:ID="PHO-387392">
>
>       <rdf:type
>rdf:resource="http://www.iso15926.org/part2/2003-12#PhysicalObject"/>
>
>       <rdf:type
>rdf:resource="http://www.iso15926.org/part4/2005-10#MalePerson"/>
>
></owl:Thing> 
>
> 
>
>(if PHO-387392 had been myCar, then it would read:
>
><owl:Thing rdf:ID="PHO-387392">
>
>       <rdf:type
>rdf:resource="http://www.iso15926.org/part2/2003-12#PhysicalObject"/>
>
>       <rdf:type rdf:resource="http://www.iso15926.org/part4/2005-10#Car"/>
>
></owl:Thing> 
>
>)  (where actually the identification of MalePerson and Car would read
>something like COP-436327 and COIPO-438212, where COP=ClassOfPerson and
>COIPO-ClassOfInanimatePhysicalObject)
>
> 
>
> 
>
> 
>
>-----Original Message-----
>From: Ivan Herman [mailto:ivan@w3.org] 
>Sent: Friday, October 28, 2005 3:08 PM
>To: Hans Teijgeler
>Cc: 'Frank Manola'; semantic-web@w3.org; Paap, Onno
>Subject: Re: owl:Thing and RDF
>
>-------- Original Message --------
>
>From: "Hans Teijgeler" <hans.teijgeler@quicknet.nl>
>
>To: "'Frank Manola'" <fmanola@acm.org>
>
>CC: "'Herman, Ivan'" <ivan@w3.org>, semantic-web@w3.org, "Paap, Onno"
>
><onno.paap@ezzysurf.com>
>
>Subject: Re:owl:Thing and RDF
>
>Date: 28/10/2005 08:08
>
> 
>
>> Thanks, Frank, it is crystal clear to me now.
>
>> I hope Ivan agrees.
>
> 
>
>Yep... this is, indeed, a question of taste and readability. For outside
>user of
>
>a large RDF dataset using owl:Thing may make things (sic!) easier to read
>and
>
>comprehend. I tend to avoid to much implicit knowledge in these syntactical
>
>choices, but that may be only me.
>
> 
>
>Ivan
>
> 
>
> 
>
> 
>
>> Hans
>
>> 
>
>> ===========================================
>
>> 
>
>> -----Original Message-----
>
>> From: semantic-web-request@w3.org [mailto:semantic-web-request@w3.org] On
>
>> Behalf Of Frank Manola
>
>> Sent: Thursday, October 27, 2005 11:36 PM
>
>> To: Hans Teijgeler
>
>> Cc: Herman, Ivan; semantic-web@w3.org
>
>> Subject: Re: owl:Thing and RDF
>
>> 
>
>> 
>
>> Hans--
>
>> 
>
>> See embedded comments below.
>
>> 
>
>> Hans Teijgeler wrote:
>
>> 
>
>>>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...
>
>>> 
>
>>>Ivan
>
>>>=========================================
>
>>>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.
>
>>> 
>
>>>--Frank
>
>>>=============================================
>
>>> 
>
>>>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?
>
>>> 
>
>> 
>
>> 
>
>> I'm not sure I understand your concern.  If the problem is that there
>
>> are equivalent ways to say the same thing in the SW, and you expect
>
>> there to be only one way, I don't think that's a very realistic
>
>> expectation if the SW is to get anywhere expressing reasonably complex
>
>> things.  After all, there are certainly lots of ways to say the same
>
>> thing in English (or Dutch, or C), right?
>
>> 
>
>>>Frank, if I would follow Ivan's advice, and typically use something
>
>>>explicit like:
>
>>> 
>
>>>    <owl:Thing rdf:ID="PHO-387392"/>
>
>>>    <owl:Thing rdf:about="#PHO-387392">
>
>>>        <rdf:type
>
>>>rdf:resource="http://www.iso15926.org/part2/2003-12#PhysicalObject"/>
>
>>>        <rdfs:label>Joe Blogg</rdfs:label>
>
>>>    </owl:Thing>
>
>>> 
>
>>>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).
>
>>> 
>
>> 
>
>> 
>
>> Perhaps I'm missing something (or I didn't explain myself very well),
>
>> but I don't really understand the dilemma.  Of course you can use the
>
>> syntax above (and I don't really think that it "neglects" RDF in any
>
>> awful way!).  The only possible disadvantage I see is extra syntax.
>
>> There is an example in Section 3.1.2 of the OWL Guide
>
>> (http://www.w3.org/TR/owl-guide/) that seems to exactly parallel your
>
>> example.  In that example, the Guide notes that, in defining an
>
>> instance, the syntax
>
>> 
>
>>    <Region rdf:ID="CentralCoastRegion" />
>
>> 
>
>> is exactly equivalent in meaning to
>
>> 
>
>>    <owl:Thing rdf:ID="CentralCoastRegion" />
>
>> 
>
>>    <owl:Thing rdf:about="#CentralCoastRegion">
>
>>       <rdf:type rdf:resource="#Region"/>
>
>>    </owl:Thing>
>
>> 
>
>> Thus it seems to me that instead of writing your example
>
>> 
>
>>     <owl:Thing rdf:ID="PHO-387392"/>
>
>> 
>
>>     <owl:Thing rdf:about="#PHO-387392">
>
>>        <rdf:type
>
>> rdf:resource="http://www.iso15926.org/part2/2003-12#PhysicalObject"/>
>
>>        <rdfs:label>Joe Blogg</rdfs:label>
>
>>     </owl:Thing>
>
>> 
>
>> you could write it instead as something like:
>
>> 
>
>>    <iso:PhysicalObject rdf:ID="PHO-387392">
>
>>       <rdfs:label>Joe Blogg</rdfs:label>
>
>>    </iso:PhysicalObject>
>
>> 
>
>> (where iso: is the namespace prefix that gives you the rest of the full
>
>> ISO URI).  This is a typical RDF "typed node" abbreviation, and it works
>
>> the same way in OWL (as an RDF language).  This is what I meant by
>
>> saying I didn't see the need to use owl:Thing explicitly.
>
>> 
>
>> I'm assuming that http://www.iso15926.org/part2/2003-12#PhysicalObject
>
>> is already defined as an OWL class, since your original message spoke of
>
>> rdf:typing the instances with the applicable OWL classes.  That being
>
>> the case, if you define the instance as an instance of that OWL class,
>
>> the OWL semantics specify that it's also an instance of owl:Thing,
>
>> without you having to explicitly say so.  Thus as I see it the issue
>
>> isn't about whether or not you want to be rigorous in distinguishing
>
>> instances from classes (doing so is always a good idea), it's about
>
>> whether or not you want to take advantage of built-in OWL semantics to
>
>> simplify the syntax you write.
>
>> 
>
>> However, as I said above, I may be missing something, and it won't hurt
>
>> to write owl:Thing explicitly 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?
>
>>> 
>
>> 
>
>> No problem.  Lots of things are identified (for given applications) by
>
>> non-human understandable names (very few people refer to me in
>
>> conversation by my drivers license number, although the Registry of
>
>> Motor Vehicles insists that I have one anyway).
>
>> 
>
>> Cheers.
>
>> --Frank
>
>> 
>
>> 
>
>>>Regards,
>
>>>Hans
>
>> 
>
>> 
>
>> 
>
> 
>
>--
>
> 
>
>Ivan Herman
>
>W3C Communications Team, Head of Offices
>
>C/o W3C Benelux Office at CWI, Kruislaan 413
>
>1098SJ Amsterdam, The Netherlands
>
>tel: +31-20-5924163; mobile: +31-641044153;
>
>URL: http://www.w3.org/People/Ivan/
>
>
Received on Sunday, 30 October 2005 11:46:37 UTC

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