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John Cowan wrote:
> Thomas B. Passin scripsit:
>
> > I think that much confusion has arisen when non-retrievable URIs got
into
> > the mix. On top of this, RDF uses the term "Resource" in a specialized
way,
> > so that it does not really mean the same thing as a "resource" in the
first
> > story. When a URI is non-retrievable and is used to "identify"
something
> > non-retrievable - it may be the Yosemite valley or some intangible
concept
> > or whatever, then there is no act of emitting a representation that is
ever
> > going to happen.
>
> Ah, but there is. There is no *intrinsic* difficulty in
> saying that what you get when you perform a GET on the URI
> http://www.ibiblio.org/wm/paint/auth/vinci/joconde/joconde.jpg ,
> for example, is a representation not merely of a particular document,
> but of a particular painting, and for that matter a particular woman.
> Neither the model nor the painting are on the network, of course. These
> reps of reps and reps of reps of reps are where the difficulties arise.
Correct. Either 1) resource as document, or 2) resource as subject of
document, might be correct as it is currently defined. In the interest of
settling this ambiguity perhaps it is best to settle on 1) resource as
document, or better as TimBL recently says: "information resource", that is
all HTTP URIs identify "information resources" (this is sense 1).
>
> The question then is: when we use that URI as the subject (WLG) of an
> RDF triple, which of the three are we predicating about? The document,
> the painting, or the woman? RDF makes it impossible to say.
Actually RDF/OWL makes it really easy to say, assert an rdf:type on the URI
e.g. one could say:
<http://www.ibiblio.org/wm/paint/auth/vinci/joconde/joconde.jpg> rdf:type
document:jpeg .
or one could alternatively say:
<http://www.ibiblio.org/wm/paint/auth/vinci/joconde/joconde.jpg> rdf:type
art:painting .
or one could alternatively say:
<http://www.ibiblio.org/wm/paint/auth/vinci/joconde/joconde.jpg> rdf:type
bio:woman .
and in OWL you can say that documents, paintings and women are disjoint
classes of things i.e.
document:jpeg owl:disjointWith bio:woman .
>
> Topic maps at least sharply distinguish between assertions about documents
> and assertions about the subject matter of documents, though it remains
> outside the system whether a JPEG such as this has the painting or the
> woman as its subject matter.
>
Can one derive inferences from Topic Maps, that one could not similarly
derive from an OWL ontology? RDF/OWL makes these sorts of sharp distinctions
quite easy.
Jonathan
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