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Re: namedNode? in predicate position?

From: Dan Brickley <danbri@w3.org>
Date: Mon, 3 Sep 2001 09:03:09 -0400 (EDT)
To: Art Barstow <barstow@w3.org>
cc: Aaron Swartz <aswartz@upclink.com>, Dave Beckett <dave.beckett@bristol.ac.uk>, <w3c-rdfcore-wg@w3.org>
Message-ID: <Pine.LNX.4.30.0109030856170.8261-100000@tux.w3.org>
On Mon, 3 Sep 2001, Art Barstow wrote:

> On Sun, Sep 02, 2001 at 01:36:42AM -0500, Aaron Swartz wrote:
> > On Wednesday, August 29, 2001, at 09:27  AM, Dave Beckett wrote:
> >
> > >> while at next telecon agenda items,
> > >> what about the N-triples/MT related questions
> > >> 1. predicate ::= uriref  versus predicate ::= uriref | namedNode?
> > >
> > > Does RDF allow, let's call it, non-URI-ref for predicates?
> > > I don't think so, at present.  In the graph model in the original
> > > M&S, predicates are arrows with URIs, they are never empty circles.
> >
> > Well maybe it's an arrow without a URI.
> >
> I like the idea of allowing predicates to be princeNodes
> because it would eliminate special casing predicates (and simplify
> N-Triples a little).  However, I agree with Dave's position (although
> M&S is not explicit on this) and thus have written some apps that
> assume predicates will be URI-refs and not princeNodes.
>
> > I think that princeNodes should be allowed in the predicate
> > slot... they're rather useful.
>
> Would you please give an example where this would be useful?

Representing partial knowledge: for example, one might know that persons A
and B were related biologically, without knowing whether that was
brother/sister/father etc. Being able to represent claims about a
relationship that holds between A and B (without URI-naming that relation)
could be useful. You could say, for example, that there is a relationship
that holds between A and B, and that the relationship was of rdf:type
misc:BiologicalRelativeRelation. Where misc:brother, misc:sister etc were
members of that class.

Sorry for the cheeseball example, I'm in a rush. Another more general
example could probably be composed that used WebOnt / DAML+OIL classes
such as daml:UniqueProperty.

Also for the record, none of my code has any problem with un-named
relations, although I've assumed there was no way to serialize this in
RDF/XML 1.0.

Dan
Received on Monday, 3 September 2001 09:03:13 EDT

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