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Re: Possible URI collisions with graph URIs

From: Peter Ansell <ansell.peter@gmail.com>
Date: Fri, 6 May 2011 07:22:09 +1000
Message-ID: <BANLkTi=Y11u95ez0LuzGXvNLLzrCN5ivtQ@mail.gmail.com>
To: Kjetil Kjernsmo <kjetil@kjernsmo.net>
Cc: public-sparql-dev@w3.org
On 5 May 2011 21:57, Kjetil Kjernsmo <kjetil@kjernsmo.net> wrote:
> Dear all,
> I've been concerned with the problems caused by the SPARQL 1.0 concept of what
> the graph URI identifies, something I find terribly confusing and if it is
> brought to SPARQL 1.1, I think that it will cause much confusion in the years
> to come. Rather than send yet another comment, I figured I'll rather post a
> question that may help to clearify things.
> The confusion is caused by the formulation in the last paragraph of section
> 8.2.2 of the 1.0 query language spec:
>  http://www.w3.org/TR/rdf-sparql-query/#namedGraphs
> as I have previously commented. With 1.0, it wasn't hard to live with that
> confusion, is nothing specified what you should do if it was dereferenced.
> You could get around any conflicts by clever use of redirects or something.
> Now that the Graph Store HTTP Protocol does attempt to specify what to do, it
> changes the game somewhat.
> To me, it seems to boil down to what URI collisions may occur. I would like to
> ask, for each of the below triples, given that http://example.org/graph
> identifies a graph and returns a 200 when dereferenced, which of these
> triples (prefixes omitted for brevity) would introduce a URI collision, and
> why or why not?
> <http://example.org/graph> a foaf:PersonalProfileDocument .
> <http://example.org/graph> a void:Dataset .
> <http://example.org/graph> a owl:Ontology .
> <http://example.org/graph> a cc:Work .
> All of these are very common, and I sincerely hope that the answer is "none of
> them introduce a URI collision", but in that case, I hope someone can explain
> it in clear terms. :-)
> Finally, I also note that is commonly implemented that you can do
> SELECT * FROM <file:///home/foo/data.ttl> WHERE { ?s ?p ?o }
> In this case, you can say that file:///home/foo/data.ttl identifies a file
> without introducing a URI collision, or is this bad practice?

If you want to store information about the file, independent of the
triples in the file, you could do it in a separate graph that is
dedicated to this purpose. A URI collision is then only important if
the triples in the file are inconsistent because your added statements
are not colocated.


Received on Thursday, 5 May 2011 21:22:37 UTC

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