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Re: Scope of blank nodes in TriG?

From: Ian Davis <ian.davis@talis.com>
Date: Fri, 14 Oct 2011 12:35:20 +0100
Message-ID: <CAAiX05F6BqANi2r7VmtWO1b5yLtmHvQpq4VdMYZrsk_poWUBOA@mail.gmail.com>
To: Steve Harris <steve.harris@garlik.com>
Cc: William Waites <wwaites@tardis.ed.ac.uk>, public-rdf-wg@w3.org
On Fri, Oct 14, 2011 at 12:17 PM, Steve Harris <steve.harris@garlik.com> wrote:
>
> On 2011-10-14, at 12:12, William Waites wrote:
>
> > On Fri, 14 Oct 2011 11:57:43 +0100, Ian Davis <ian.davis@talis.com> said:
> >
> >    iand> I think  it does matter. What was the N-Quads document that
> >    iand> was thew result of the conversion.
> >
> > I just looked up the mime type for trig, and did it directly with the
> > same results. The reason I thought it wouldn't matter is because I
> > suspected (correctly) that both documents would get parsed into the
> > same internal represenatation by raptor which is what actually gets
> > put into the store.
>
> Somewhat off topic, but from memory I don't think that's correct.
>
> I think Trig generates graph change callbacks, and N-Quads emits quads.
>
> 4store (apparently) treats them the same, but it doesn't have to.
>
> - Steve


I think the TriG spec could be updated by the authors so blank nodes
are scoped to the document rather than the graph. It just seems like a
bug in the spec to me.

This WG probably ought to decide on the semantics of blank nodes
appearing in multiple graphs in a dataset.

There is a material difference between the bahaviour of parsing the
single nquads file into a dataset:

_:bnode <http://example.com/p> "foo" <http://example.com/g1> .
_:bnode <http://example.com/p> "bar" <http://example.com/g2> .

and parsing two separate nquads files:


file1.nq:

_:bnode <http://example.com/p> "foo" <http://example.com/g1> .


file2.nq:

_:bnode <http://example.com/p> "bar" <http://example.com/g2> .


There is also the case to consider where the following ntriples file
is found at <http://example.com/g1>

_:bnode <http://example.com/p> "foo" .

and the following is found at <http://example.com/g2>

_:bnode <http://example.com/p> "bar" .



Ian

--
Ian Davis, Chief Technology Officer, Talis Group Ltd.
http://www.talis.com/ | Registered in England and Wales as 5382297
Received on Friday, 14 October 2011 11:35:57 GMT

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