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Re: abstract class

From: Marc Carrion <marc_carrion@yahoo.es>
Date: Thu, 23 Jan 2003 14:16:54 -0800 (PST)
Message-ID: <20030123221654.85814.qmail@web11906.mail.yahoo.com>
To: Brian McBride <bwm@hplb.hpl.hp.com>, marc@jfcarrion.com, www-rdf-comments@w3.org


--- Brian McBride <bwm@hplb.hpl.hp.com> wrote:
> 
> Hi Marc,
> 
  Hi Mr. Brian

> This message has been posted to the RDF comments
> mailing list and I note 
> also the discussion on RDF interest beginning with:
> 
>   
>
http://lists.w3.org/Archives/Public/www-rdf-interest/2003Jan/0140.html
> 
> I understand that what you would like to be able to
> do is to express the 
> fact that given:
> 
>    sc1 rdfs:subClassOf c .
>    sc2 rdfs:subClassOf c .
>    c   rdf:type        rdfs:Abstract .
> 
> there are no instances of c that are not instances
> of either sc1 or sc2.
  More or less, I would like to say that I don't have
instances of c, that would be enough.
 
> This is fraught with difficulties for a number of
> reasons:
> 
>    1. you want to express a negation.  that is
> beyond the expressive power 
> of RDF, and would be a major change to introduce.
  I know negation would imply changes that are not
affordables by now, I'm not saying that.

>    2. you want to express a closed world assumption.
>  how do I know that 
> there is not an sc3 that you just haven't told me
> about.
  I don't want a clossed world. If some sc3 is
subclassof c it's ok for me.
 
> If you need this sort of expressive power, then you
> need a powerful 
> language such as daml+oil or owl.
  We thought RDF is powerful enough for our needings,
we thought it would be more powerful with some new
features, no big changes.
 
> At 07:27 23/01/2003 -0800, Marc Carrion wrote:
> 
> [...]
> 
> > > >
> > > >    PS: Just a thought. 'rdfs:seeAlso'
> > > 'rdfs:domain'
> > > >is 'rdf:Resource', the last resource defined in
> the
> > > >new schema
> > > >       <rdf:Description
> > >
> >rdf:about="http://www.w3.org/2000/01/rdf-schema#">
> > > >          <rdfs:seeAlso
> > >
> >
>
>rdf:resource=http://www.w3.org/2000/01/rdf-schema-more#"/>
> > > >       </rdf:Description>
> > > >         http://www.w3.org/2000/01/rdf-schema#
> is
> > > not
> > > >a 'rdf:Resource',
> 
> On what basis do you say that?  To RDF, anything
> identified by an RDF URI 
> Reference is a resource.
  I based on the fact that all Classes we define in
our model are subclass of Resource, and we say it, we
don't supose it. You can see it in the rdfs schema,
some examples:

<rdfs:Class
rdf:about="http://www.w3.org/2000/01/rdf-schema#Class">
  <rdfs:isDefinedBy
rdf:resource="http://www.w3.org/2000/01/rdf-schema#"/>
  <rdfs:label xml:lang="en">Class</rdfs:label>
  <rdfs:comment>The concept of Class</rdfs:comment>
  <rdfs:subClassOf
rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
</rdfs:Class>

<rdfs:Class
rdf:about="http://www.w3.org/1999/02/22-rdf-syntax-ns#Property">
  <rdfs:isDefinedBy
rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#"/>
  <rdfs:label xml:lang="en">Property</rdfs:label>
  <rdfs:comment>The concept of a
property.</rdfs:comment>
  <rdfs:subClassOf
rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
</rdfs:Class>

  If anything identified with a RDF URI it's a
Resource, why all the classes I define should extend
from resource?
 
  (I think the problem is we are using the same word
for the resource in the model and for the object
resource in the schema)

> Brian
> 
  Thanks very much for your attention,
                                     Marc

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Received on Thursday, 23 January 2003 17:16:55 GMT

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