W3C home > Mailing lists > Public > www-webont-wg@w3.org > May 2003

proposed interim response for ``Comments from RDFCore on S+AS''

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 09 May 2003 14:52:12 -0400 (EDT)
Message-Id: <20030509.145212.17063300.pfps@research.bell-labs.com>
To: www-webont-wg@w3.org



> The RDFCore WG has me to forward the comments below on their behalf.  Other 
> comments, on behalf of RDFCore will be sent in separate messages.
> 
> Brian
> 
> ------------------------------
> 
> owlsas-rdfcore-np-complete
> 
> RDFCore notes the a consequence of the rules for owl:equivalentClass is
> that distinguishing OWL DL from OWL Full has complexity NP complete and
> suggests WEBONT investigate whether this complexity can be reduced.

This is currently being investigated.  We expect that the situation will
change.  

> We note from the RDF semantics document
> 
> [[
> Specifications of such syntactically restricted semantic extensions MUST 
> include a specification of their syntactic conditions which are sufficient 
> to enable software to distinguish unambiguously those RDF graphs to which 
> the extended semantic conditions apply.
> ]]
>    http://www.w3.org/TR/rdf-mt/

Hmm.  I'm not sure what the point of this note is.

> -------------------------------
> 
> owlsas-rdfcore-bnodes-restrictions
> 
> RDFCore are concerned that restrictions placed on b-nodes will limit the
> applicability of OWL DL to an unnecessarily restricted subset of RDF
> instance data, for which no such restrictions apply.
> 
> For example, consider the use case in:
> 
>    http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003May/0109.html
> 
> [[
> If bNodes can only be used as the object of a single triple, they lose most
> of their value as a construct in the language. As does rdf:nodeID for that
> matter.
> 
> <Image>
>   <depicts>
>    <Person>
>      <mbox rdf:resource="mailto:danbri@w3.org"/>
>    </Person>
> </Image>
> 
> <Group>
>   <member>
>    <Person>
>     <homepage rdf:resource="http://www.w3.org/People/DanBri/"/>
>    </Person>
>   </member>
> </Group>
> 
> ...is OK in OWL, but if we add in an rdf:nodeID on the two Person elements
> to express that they serialize descriptions of the same (un-named) resource,
> we're in trouble? Ouch. That breaks most of my uses of RDF, and a lot of
> deployed FOAF documents.
> ]]
> 
> 
> Specifically we request, that in Owl DL and Owl lite:
> 
>    a) that a b-node representing an individual may be the object of more
> than one triple
>    b) that cycles of b-nodes representing individuals be allowed.

We note that this is a restriction that until recently has also been in
RDF.  It is thus hard for us to see how this can break any significant
number of deployed uses of RDF.
Received on Friday, 9 May 2003 14:52:22 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:58:00 GMT