W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > May 2003

Re: restrictions bnodes

From: Dan Brickley <danbri@w3.org>
Date: Fri, 9 May 2003 09:14:42 -0400
To: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Cc: Jan Grant <Jan.Grant@bristol.ac.uk>, Brian McBride <bwm@hplb.hpl.hp.com>, graham Klyne <gk@ninebynine.org>, RDF Core <w3c-rdfcore-wg@w3.org>
Message-ID: <20030509131442.GD21436@tux.w3.org>

* Jeremy Carroll <jjc@hplb.hpl.hp.com> [2003-05-09 14:18+0200]
> 
> 
> > -----Original Message-----
> > If the restriction is that individuals can't be the _object_ of multiple
> > triples, we could use an inverse of the 'depicts' of 'member'
> > property instead,
> > but that's an ugly hack. Is this restriction across all of OWL,
> > or just the
> > DL & Lite dialects?
> 
> Only OWL DL and OWL Lite.

Phew
> 
> 
> A workaround is as follows.
> 
> <rdf:RDF xml:base="&my;"
>   xmlns:my="&my;" >
> <owl:InverseFunctionalProperty rdf:about="#nodeID" />
> <Image>
>  <depicts>
>   <Person>
>     <my:nodeID rdf:resource="gensym001"/>
>     <mbox rdf:resource="mailto:danbri@w3.org"/>
>   </Person>
> </Image>
> 
> <Group>
>  <member>
>   <Person>
>    <my:nodeID rdf:resource="gensym001"/>
>    <homepage rdf:resource="http://www.w3.org/People/DanBri/"/>
>   </Person>
>  </member>
> </Group>

That's a workaround that works at the OWL layers, but takes away the 
ability for RDF/S tools to be able to answer questions like 
"what groups is this person in, and what's his/her homepage?". By making 
things more acceptable to OWL tools, we make them less scrutable to RDF. A 
painful tradeoff. For FOAF, it's bearable as we use owl:InverseFunctionalProperty
a lot anyway. But this isn't (yet...) common practice. Many RDF parsers are
acquiring rdf:nodeID support; not so many tools do merging on InverseFunctionals
yet.
 

> This forces the two Persons to refer to the same resource, even though they
> have different bnodes. You do need to pollute the URI space with the
> gensym's, as far as I can tell. (You cannot use strings with
> InverseFunctionalProperty's in OWL DL and OWL Lite).

Oh, I think I knew that and was trying to forget it. Yet more evidence that
the DL/Lite profile of OWL will turn out to be of niche interest, imho. So long 
as it's allowed in OWL Full I can contain my dissapointment...

Dan
Received on Friday, 9 May 2003 09:14:58 EDT

This archive was generated by hypermail pre-2.1.9 : Wednesday, 3 September 2003 09:57:29 EDT