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Re: Implementing statement grouping, contexts, quads and scopes (was: Re: Out of context, in context, out of subject ????)

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Mon, 24 Jun 2002 10:47:54 +0300
To: ext Jonathan Borden <jonathan@openhealth.org>, <areggiori@webweaving.org>, Didier <didier@phpapp.org>
CC: RDF Interest <www-rdf-interest@w3.org>, RDF Logic <www-rdf-logic@w3.org>
Message-ID: <B93CA95A.173C9%patrick.stickler@nokia.com>

On 2002-06-21 15:53, "ext Jonathan Borden" <jonathan@openhealth.org> wrote:

> The concept of "dark triples" as a layering option seems to be getting a bit
> misunderstood. The essence of "dark" or "unasserted" triples is simply that,
> from a technical perspective, it is difficult (some would indeed say
> impossible) to define a language such as OWL (and given the constraints
> placed on this language by the WebOnt charter etc.) in RDF if OWL is to have
> the characteristics we desire, and RDF triples are all "truths".

I consider RDF to already have a mechanism for expressing unasserted
triples, namely reification. The only reason folks want to create something
else, IMO, is simply because the RDF/XML syntax is so obese. I.e.

   <rdf:Statement>
      <rdf:subject   rdf:resource="#foo"/>
      <rdf:predicate rdf:resource="&owl;bar"/>
      <rdf:object    rdf:resource="#bas"/>
   </rdf:Statement>

It seems to me that the solution is simply to add a contracted form
of reification, to make the existing mechanism more palatable. E.g.

   <rdf:Statement rdf:about="#foo">
      <owl:bar rdf:resource="#bas"/>
   </rdf:Statement>

Yes, this is a (minor) change to RDF/XML parsing, but IMO a far
cheaper cost than any of the other proposals on the table for
signaling "dark" triples. Note that it does not constitute a
change to the RDF syntax, only to the special interpretation
of rdf:Statement in contracted rather than full form. I.e it's
only a change to the RDF/XML parsing algorithm. And since all
RDF parsers are going to *have* to be revised to support the
already adopted changes to RDF/XML, this is not a big deal.

What more does OWL (or any other layer) need? An OWL application is
then free to treat unasserted RDF statements employing OWL predicates,
as asserted at the OWL layer, without any impact at all to RDF-only
applications and without requiring RDF-only applications to know
anything about any higher layers or (most importantly) needing to
explicitly know which predicates in otherwise RDF asserted triples
are "dark" and must actually be treated as unasserted at the
RDF layer (what nonsense).

Regards,

Patrick

--
               
Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Monday, 24 June 2002 03:43:29 GMT

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