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RE: owl:Thing and RDF

From: Hans Teijgeler <hans.teijgeler@quicknet.nl>
Date: Sun, 30 Oct 2005 09:57:02 +0100
Message-Id: <200510300857.j9U8v6hA006179@vmx80.multikabel.net>
To: "'Ivan Herman'" <ivan@w3.org>
Cc: "Manola, Frank" <fmanola@acm.org>, <semantic-web@w3.org>, "Paap, Onno" <onno.paap@ezzysurf.com>
Hi Ivan,


Would this be acceptable:

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








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"/>


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">





(if PHO-387392 had been myCar, then it would read:

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


       <rdf:type rdf:resource="http://www.iso15926.org/part4/2005-10#Car"/>


)  (where actually the identification of MalePerson and Car would read
something like COP-436327 and COIPO-438212, where COP=ClassOfPerson and




-----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"


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

comprehend. I tend to avoid to much implicit knowledge in these syntactical

choices, but that may be only me.






> 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...




>>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?




> 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


>>        <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











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 08:57:41 UTC

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