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Re: #rdfms-identity-anon-resources: provenance

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Tue, 24 Jul 2001 11:18:05 +0100
Message-ID: <3B5D4B5D.DB1EC084@hplb.hpl.hp.com>
To: pat hayes <phayes@ai.uwf.edu>
CC: w3c-rdfcore-wg@w3.org

pat hayes wrote:
> >I was chatting with a colleague to day and the subject of anon resources
> >and provenance came up.
> >
> >Assume I recieve the following rdf from some source SOURCE, possibly with a
> >digital signature:
> >
> >  <rdf:Description>
> >    <foo:bar>foobar</foo:bar>
> >  </rdf:Description>
> >  <rdf:Description rdf:about="http://goo">
> >    <foo:bar><foobar</foo:bar>
> >  </rdf:Description>
> >
> >If were to represent this in my machine as:
> >
> >  <gensym:1234> <foo:bar> "foobar" .
> >  <http://goo>  <foo:bar> "foobar" .
> >
> >this is not the information that SOURCE signed - SOURCE made no assertion
> >about <gensym:1234>.  We'd have to be able to distinguish between the
> >gensym'd URI and the 'real' one.
> As I said a while ago,

I'm struggling slowly to understand.  My appologies if I miss the
significance of some remarks first time around.

> it matters who generates the gensym. If SOURCE
> uses an anonymous node (existential quantifier) then indeed you are
> not entitled to replace it with a gensym and say that it represents
> what SOURCE said.

The syntax clearly allows anonymous resources.  I think you have just
said that a parser, which on receiving RDF/XML containing anon
resources, assigned URI's to the anon resources when spitting out the
triples would not be representing exactly the information it had
as input.  Are we agreeing on this?

To represent exactly the information recieved, anon resources must
be a part of the model/abstract syntax.  Yes? No?

> That is what the logic says also: the step from the
> existential to the skolem form is *not* a valid inference, so you
> would not be correct in saying that conclusion followed from what
> SOURCE said. However, SOURCE could have replaced his existential with
> a skolem constant

Could have, but didn't.  I suggest the requirement here is that
the abstract syntax/model be able to represent *exactly* the information
conveyed in the syntax.

> ( a newly generated URI, guaranteed different from
> any other URI anywhere else) and, my claim is, that you would have
> been told virtually the same content by SOURCE under those
> circumstances as you would have been by SOURCE telling you his
> existential. (Not quite *exactly* the same, since you would know, in
> addition to the fact that the thing exists, that SOURCE was using
> this URI to refer to it. But that information wouldnt help you make
> any inferences about the thing that you couldnt have made from the
> existential.) But indeed, if someone signs a document then it isnt,
> in general, correct to transfer that signature to another document
> that differs even in the slightest respect, so the issue of whether
> the inferences are valid or not may be irrelevant here.

My point here is that the abstract model should be able to represent
*exactly* the information that SOURCE intended to sign.  Any subsequent
inferences are the responsibility of the recipient.

Received on Tuesday, 24 July 2001 06:20:40 UTC

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