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Re: What's the difference? rdf:about, owl:sameIndividualAs

From: Thomas B. Passin <tpassin@comcast.net>
Date: Sun, 25 May 2003 17:20:51 -0400
To: www-rdf-logic@w3.org
Message-id: <006b01c32303$84b9f7c0$6401a8c0@tbp1>

[Thomas B. Passin]

Whoops, I did not quite write what I meant here.
>
> [Jimmy Cerra]
>
> >
> > What's the difference between rdf:about and owl:sameIndividualAs?  They
> > all seem to be used to define a resource.
>
> From both a formal and a modeling point of view, they are very different.
> rdf:about is a syntactical device to identify the subject of a triple in a
> serialized RDF graph.  owl:sameIndividualAs is a predicate, used as part
of
> a triple to assert a statement.  Whether or not you think that kind of
> assertion is always sensible to make is another thing althogether.
>
> Take the following example:
> >
> > <owl:Thing rdf:about="uri#foo" />
> >
> > That serialized RDF statement says that a resource, identified by
> > "uri#foo", is an individual (as defined by OWL).
>
> It can be any resource.  It could be a class.

I was thinking of a class considered as an individual, which is allowed in
OWL full.

> Right, it has the effect of
> an empty statement about uri#foo.
>
>  However, I could also
> > say that a blank node that is identical to the resource identified by
> > "uri#foo" is an individual:
> >
>
> > <owl:Thing>
> > <owl:sameIndividualAs rdf:resource="uri#foo" />
> > </owl:Thing>
> >
> > From that statement, an agent should conclude that the resource
> > identified by "uri#foo" has the same properties as that blank node.
>
> You just asserted that owlThing, a predefined class, is the same
individual as uri#foo.
> From that, if I do not know anything else about uri#foo, I could infer
that
> the node uri#foo is the same node as the node representing &owl;#Thing (or
> whatever the right URI is)
>

However, since owl:Thing is supposed to be a class, there may be a
contradiction.  I overlooked this on the last post, thinking about the class
as an individual.  At any rate, using sameIndividualAs on a  node, blank or
not,  either identifies it as the same node as another, or there is a
contradiction.  It still has nothing to do with rdf:about.

> > Since the blank node is an individual,
>

So delete this next ...
> We only knew it is a Resource...
>
> > then the resource identified by
> > "uri#foo" must have the same properties - mainly that it is an
> > individual.
>

... and this
> No, just a Resource.
>

> So rdf:about and owl:sameIndividualAs can be used to
> > identify a resource; the former by direct statements and the latter by
> > inference.
> >

And this still stands ...
>
> There are many ways to identify resources by inference.  That does not
mean
> that all statements that feed those inference are equivalent.  Anyway,
> rdf:about  is not a resource or property, so they are not equivalent.
> Besides that, the sense in which rdf:about "identifies" a resource is very
> different - it indicates in the serialization which node to construct or
to
> attach an arc to.  The predicates represent, of course, the arcs
themselves.
> So there is no way the two are the "same thing" or equivalent.  One is a
> construction device, one is a part of a graph.
>
Cheers,

 Tom P
>
Received on Sunday, 25 May 2003 17:19:17 GMT

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