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Re: Scope of blank nodes in TriG?

From: William Waites <wwaites@tardis.ed.ac.uk>
Date: Fri, 14 Oct 2011 11:45:20 +0100 (BST)
Message-Id: <20111014.114520.519943541.wwaites@tardis.ed.ac.uk>
To: ian.davis@talis.com
Cc: public-rdf-wg@w3.org
On Fri, 14 Oct 2011 10:45:34 +0100, Ian Davis <ian.davis@talis.com> said:

    iand> Example Document 3 in the TriG spec[1] shows the same blank
    iand> node label being used in different graphs. My interpretation
    iand> of the example is that those blank nodes are distinct,
    iand> i.e. the scope of blank node labels is the graph not the
    iand> TriG document. How do the main graph stores behave? Is it
    iand> possible to put the same blank node into two different
    iand> graphs? If so, this information would not be serializable in
    iand> TriG if my interpretation is correct.

I agree with your interpretation. However 4store appears to have
different behaviour here:

    @prefix ex: <http://example.org/>.

    ex:g1 {
      _:s a ex:T
    }

    ex:g2 {
      _:s a ex:T
    }

And this query:

    SELECT * WHERE {
        { GRAPH <http://example.org/g1> { ?s ?p ?o } } UNION
        { GRAPH <http://example.org/g2> { ?s ?p ?o } }
    }

Shows the bnodes as having been merged when you run it here:

    http://gallows.inf.ed.ac.uk/data/test/

(note, I converted the TriG document to N-Quads to import it but I
don't think that should matter)

-w
Received on Friday, 14 October 2011 10:46:03 GMT

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