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Re: Need a decision (was: Re: namedNode? in predicate position?)

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Wed, 05 Sep 2001 12:36:40 +0100
Message-ID: <3B960E48.7F5EBDCD@hplb.hpl.hp.com>
To: pat hayes <phayes@ai.uwf.edu>
CC: w3c-rdfcore-wg@w3.org
Hi Pat,

> I will put off further work on the MT document until this issue is decided.

That get's the blood flowing first thing in the morning.

We can make this decision independently from deciding whether prince arcs are

Whether or not we decide to allow prince arcs, we should adopt a notation
that would allow them to be representated.  That way any future WG, (and ours)
is free to decide that they are allowed, without having to revamp the
core representation.

We decided at the F2F to use a graph notation.  If we can *reasonably* extend
that notation to support prince arc's I suggest we stick with the decision
we made.  

To extend the graph notation we'd need:

  o non-URI identifying labels on arcs
  o a node and an arc can have the same label
  o a scoping notation

Is that sufficient?  If it is, is it a reasonable notation on which to base
the formal semantics?


ps: If I may say so, Pat, that was a very good catch.


pat hayes wrote:
> Dave Beckett <dave.beckett@bristol.ac.uk>
> > >>>Art Barstow said:
> >
> ><snip/>
> >
> > > 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 don't have any problem with the change - just to note it *is* a
> >change and we should take care that if we do this, we have good
> >reasons and consider what the change causes deployed applications.
> >
> >The current RDF/XML syntax cannot generate any model with non-URI-ref
> >predicates (unless you reify) thus that means some models can be
> >created that can not be transfered in the standard RDF/XML syntax
> >(although this is true for other models too).
> >
> >For evidence on implementation: my Redland system has no problem
> >handling princeNode predicates.
> Please let us get this decided as quickly as possible, as if we allow
> anonymous properties then I should change the MT back to apply
> directly to N-triples rather than to RDF graphs, since not all
> N-triples documents will be graphs, and in any case (as outlined in
> my reply to Aaron), the advantages of the graph syntax would be lost
> if we make this change, so it would be better to return to a more
> conventional notion of syntax.
> In fact if we do make this change, I would urge that we decide that
> some kind of N-triplish syntax be adopted as the primary RDF syntax
> (though preferably with an explicit notion of syntactic scope), and
> abandon the 'RDF graph' idea as simply misleading, largely for the
> reasons Aaron suggests.
> I will put off further work on the MT document until this issue is decided.
> Pat Hayes
> ---------------------------------------------------------------------
> (650)859 6569 w
> (650)494 3973 h (until September)
> phayes@ai.uwf.edu
> http://www.coginst.uwf.edu/~phayes
Received on Wednesday, 5 September 2001 07:40:22 UTC

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