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Comments from RDFCore on S+AS

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Fri, 09 May 2003 18:02:44 +0100
Message-Id: <5.1.0.14.0.20030509174910.079cb278@localhost>
To: public-webont-comments@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.

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/

-------------------------------

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.

-------------------------------
Received on Friday, 9 May 2003 13:02:55 GMT

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