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Re: Possible URI collisions with graph URIs

From: Kjetil Kjernsmo <kjetil@kjernsmo.net>
Date: Sun, 8 May 2011 00:24:53 +0200
To: public-sparql-dev@w3.org
Message-Id: <201105080024.54330.kjetil@kjernsmo.net>
On Thursday 5. May 2011 23:22:09 Peter Ansell wrote:
> > 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.

That doesn't really resolve the issue I was trying to get at with that 
(somewhat tangential) comment.

RFC 1738 says that "The file URL scheme is used to designate files accessible on 
a particular host computer." and I'm not sure this maps exactly to how we use 
URIs to identify resources, nor am I positive that the definition hasn't been 
updated in a more recent RFC. What I am sure about is that most developers 
will say that a file URI identifies a file, and to tell them otherwise will cause 
a lot of head-shaking and eye rolling, something the semantic web community 
cannot affort.

Then, the point of my comment was that using FROM <file:///home/foo/data.ttl> 
means that this URI also identifies some graph content, irrespective of any 
triples in it or about it. So, to me, it seems there is a distinction here 
between the actual file, and the RDF document that represents some graph 
content. 

So, my question is whether this introduces a URI collision? And the reason why 
I'm so hung up in this issue is that with the current phrase describing what 
the Graph URI identifies, so much confusion will ensue that the WG should be 
finding something better, like the RDF WG seems to be doing.

I think. But perhaps it is just me...

Yours Confusedly,

Kjetil
-- 
Kjetil Kjernsmo
Ph.d Research Fellow, Semantic Web
kjetil@kjernsmo.net
http://www.kjetil.kjernsmo.net/
Received on Saturday, 7 May 2011 22:25:26 GMT

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