On Jun 25, 2009, at 12:28 PM, Tim Finin wrote:
Toby Inkster wrote:
On Thu, 2009-06-25 at 11:59+0200, Bernhard Schandl wrote:
However many "newbies" to RDF and ontologies are confused by
this, because the triple
foaf:Agent foaf:holdsAccount foaf:OnlineAccount .
is actually not contained in the ontology.
What needs to be communicated is that: [ a
foaf:Agent ] foaf:holdsAccount [ a foaf:OnlineAccount ] .
instead. Those triples are not actually in the ontology itself, but
will
be found (or at least implied) in any instance data that makes use of
the foaf:holdsAccount property.
The N3 statement '[a foaf:Agent] foaf:holdsAccount [a
foaf:OnlineAccount]'
seems like an intuitive way, at least to this native English speaker,
to say that the domain and range of foaf:holdsAccount are foaf:Agent
and foaf:OnlineAccount, respectively. I even like it.
But it doesn't really say this, does it?
Indeed not. Your native intuition here is relying on the English
construction of the 'anonymous subject', where "A man is mortal" means
"Take a man - any man - then that man is mortal." but not many
formalisms use that technique.
Running the statement through CWM produces:
<rdf:Description>
<rdf:type rdf:resource="http://xmlns.com/foaf/0.1/Agent"/>
<holdsAccount rdf:parseType="Resource">
<rdf:type rdf:resource="http://xmlns.com/foaf/0.1/OnlineAccount
"/>
</holdsAccount>
</rdf:Description>
Maybe I am missing some of the nuances of N3 and RDF, but I think this
defines two anonymous individuals, one which is a foaf:person (among
possibly other things) and another which is a foaf:OnlineAccount
(among possibly other things) and asserts that a foaf:holdsAccount
relations exist between them.
Exactly.
I don't think this says anything about the domain and range of
foaf:holdsAccount.
Well it implies that they are respectively not actually disjoint with
foaf:person and foaf:OnlineAccount. But that's all it says.
If we interpret this as OWL, I guess we can infer
that the domain and range are subsumed by owl:Thing.
You knew that already, its tautologous.
Pat
Or maybe I am missing something.
Tim
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