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RE: rdf:nodeID and external entities?

From: Graham Klyne <GK@ninebynine.org>
Date: Tue, 14 Jan 2003 14:20:50 +0000
Message-Id: <>
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: "www-rdf-comments" <www-rdf-comments@w3.org>

At 12:33 PM 12/14/02 +0000, Brian McBride wrote:
>>If you import that file twice, regardless of whether or not you change
>>the Name of the resource referenced by _1, the blank node _1 is *not*
>>the same resource across two different parsing activities, while the
>>named node http://www.cnn.com/ *is*.
>Well, the blank node is not a resource at all, in the sense you mean.  Its 
>a node in a graph.  The question I think you are addressing is whether one 
>can be sure its the same node in the same graph across two different 
>parsings of the same file, and I agree with you in general, one cannot.

This notation uses a nodeID convention to indicate blank nodes in the 
triples of a graph. Note that while node identifiers such as _:xxx serve to 
identify blank nodes in the surface syntax, these expressions are not 
considered to be the label of the graph node they identify; they are not 
names, and do not occur in the actual graph. In particular, two N-triples 
documents which differ only by re-naming their node identifiers will be 
understood to describe identical RDF graphs.
-- http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-mt-20030117/#nodeIDnote

It might be thought that the operation of changing a bound variable would 
be an example of an inference which was valid but not covered by the 
interpolation lemma, e.g. the inference of

_:x <ex:a> <ex:b> .


_:y <ex:a> <ex:b> .

Recall however that by our conventions, these two expressions describe 
identical RDF graphs.
-- http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-mt-20030117/#entail


Graham Klyne
Received on Tuesday, 14 January 2003 12:20:02 UTC

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