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Re: Model-specific identity for anon resources, and its representation: A new issue?

From: <jos.deroo.jd@belgium.agfa.com>
Date: Thu, 14 Jun 2001 14:35:47 +0100
To: Jan.Grant@bristol.ac.uk
Cc: w3c-rdfcore-wg@w3.org
Message-Id: <OFC8D90E31.6856DB80-ON41256A6B.00461C74@bayer-ag.com>

Jan wrote:
> On Thu, 14 Jun 2001 jos.deroo.jd@belgium.agfa.com wrote:
>
> > We can imagine that anounymous terms are identified 'by their content'
> > e.g. see "more N-triples (Was RDF Statements as floating Cons Cells)"
> > http://lists.w3.org/Archives/Public/www-rdf-logic/2001Jun/0191.html
> > elaborating on that
> > [[[
> >   If an arc points to an anonymous term, then it
> >   is there 'by value' so to speak (not 'by reference').
> >   Of course one could point to constant terms
> >   and universally quantified terms used in those
> >   subgraphs, but they are 'leafs' or at the 'subgraph
> >   boundaries' so to speak.
> > ]]]
>
> This is not my intuition on this. I'm thinking purely of a graph-based
> RDF model (for the nontechnical meaning of "model"). It has nodes; some
> of those are labelled with URIs, some are not. The latter are
> "anonymous resources". Two distinct anonymous nodes may be in
> equivalent relationships with other nodes in the graph; this does not
> make them graph-theoretically equal.

That's indeed different, we imagine anonymous terms
as terms which happen to be (sub)graphs.
(so they have a 'distinction' namely the [])

> Summary: an anonymous node has its own "model-specific identity". Two
> anonymous nodes in an RDF graph may have "the same content" but still be
> distinct.

Indeed, "may have the same content" but "are different terms"
that's what we think and how we implement

> > Let's start with
> >   _:a1 <http://random.ioctl.org/#p1> _:a2 .
> >   _:a2 <http://random.ioctl.org/#p2> _:a1 .
> >
> > If you point to _:a1 via e.g.
> >   <http://random.ioctl.org/#s3> <http://random.ioctl.org/#p3> _:a1 .
> > you can see how Euler copes with such content
>
> [much Euler output snipped]
>
> > So I think both cases are representable in RDF, no?
>
> Forgive me, but if that is the case (and without adding additional
> triples), could you show me what the serialised RDF for each case looks
> like?
>
> jan (a bit slow on the uptake)

no problem Jan

case 1
------
is in RDF/n3
//////////
<http://random.ioctl.org/#s3> <http://random.ioctl.org/#p3> [ <http://random.ioctl.org/#p1> _:a2].
\\\\\\\\\\

and in RDF/xml
//////////
<!-- Processed by Id: cwm.py,v 1.54 2001/06/01 07:50:20 connolly Exp -->
<!--     using base file:/n3/testjan.n3-->


<rdf:RDF xmlns="http://random.ioctl.org/#"
    xmlns:log="http://www.w3.org/2000/10/swap/log#"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">

    <rdf:Description rdf:about="http://random.ioctl.org/#s3">
        <p3 rdf:parseType="Resource">
            <p1 rdf:parseType="Resource">
            </p1>
        </p3>
    </rdf:Description>
</rdf:RDF>
\\\\\\\\\\

case2
-----
is in RDF/n3
//////////
<http://random.ioctl.org/#feh> <http://random.ioctl.org/#p1> [ <http://random.ioctl.org/#p1> "jan"].
<http://random.ioctl.org/#yip> <http://random.ioctl.org/#p1> [ <http://random.ioctl.org/#p1> "jan"].
\\\\\\\\\\

and in RDF/xml
//////////
<!-- Processed by Id: cwm.py,v 1.54 2001/06/01 07:50:20 connolly Exp -->
<!--     using base file:/n3/testjan2.n3-->


<rdf:RDF xmlns="http://random.ioctl.org/#"
    xmlns:log="http://www.w3.org/2000/10/swap/log#"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">

    <rdf:Description rdf:about="http://random.ioctl.org/#feh">
        <p1 rdf:parseType="Resource">
            <p1>jan</p1>
        </p1>
    </rdf:Description>

    <rdf:Description rdf:about="http://random.ioctl.org/#yip">
        <p1 rdf:parseType="Resource">
            <p1>jan</p1>
        </p1>
    </rdf:Description>
</rdf:RDF>
\\\\\\\\\\

--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Thursday, 14 June 2001 08:48:31 EDT

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