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Re: Indirect Graph Identification

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 29 Nov 2011 08:40:56 -0500
To: James Leigh <james@3roundstones.com>
Cc: public-rdf-dawg-comments@w3.org
Message-ID: <1322574056.14130.337.camel@waldron>
[Now replying with public-rdf-dawg-comments@w3.org properly CC'd]

My earlier reply to your comment was informal, not the official reply
from the Working Group.   A formal reply is still forthcoming, but feel
free to continue to informal conversation to help clarify the issues.

     -- Sandro

On Tue, 2011-11-29 at 00:12 -0500, Sandro Hawke wrote:
> On Mon, 2011-11-28 at 13:55 -0500, James Leigh wrote:
> > Hello,
> > 
> > Please consider using a more general, well-known, indirect graph
> > identification[1] URI pattern.
> > 
> > The cases stated for requiring indirect graph identification are shared
> > by the Linked Data community for indirect resource identification[2].
> > Linked Data is often mirrored for the purposes of creating
> > visualizations of the data, merging some or all of the data with data
> > from other sources and/or enhancing responsiveness to queries.
> > 
> > For your convince, I have copied the indirect graph cases from
> > rdf-update[1] below.
> > 
> >       * the naming authority associated with the URI of an RDF graph in
> >         a Graph Store is not the same as the server managing the
> >         identified RDF content
> >       * the naming authority is not available
> >       * the URI is not dereferencable (i.e., when dereferenced, it does
> >         not produce a RDF graph representation)
> > 
> > Replacing "RDF graph" above with "RDF resource", the same cases are
> > equally a challenge for managing RDF data in the Linked Data community.
> > 
> > I propose that this working group consider using a more general URI
> > pattern that could be equally applied to both RDF graph storage and RDF
> > resource resolution.
> > 
> > Such a general prefix should use a well known[3] path prefix to allow
> > clients to infer the identified graph or resource without resolution.
> > The request-URI below could be recognized by both clients and servers as
> > identifying the graph with the identifier of
> > "http://www.example.com/other/graph".
> > 
> >    GET /.well-known/alias;http%3A//www.example.com/other/graph HTTP/1.1
> >    Host: example.com
> >    Accept: application/rdf+xml
> 
> I'm a big fan of .well-known, but I don't really see how it helps us
> here.
> 
> The situation here, it seems to me, is that SPARQL has created little
> pocket universes where certain IRIs (the Graph IRIs) are used in close
> proximity to RDF, tagging RDF Graph Containers, but where each IRI has
> its own local meaning.      On a single host, you could have 1000 sparql
> endpoints, each of which uses http://www.example.com/other/graph as the
> label for entirely unrelated RDF Graph Containers!
> 
> With indirect identification, those graph containers each get nice,
> normal, RDF IRIs again.  Let's say you, me, and David each have sparql
> stores on the same host, and we all use that IRI to tag OUR OWN COPY of
> some data fetched from that URL.   (I think it's a terrible practice,
> but its clear from discussions in the RDF WG that people like it and we
> can't stop it.)
> 
> So, if/when people engage in this unfortunate practice, everyone can
> still refer to their data, as if they didn't, using indirect graph
> identification, like this:
> 
>   http://www.example.com/sandro/sparql?graph=http%3A//www.example.com/other/graph
>   http://www.example.com/james/sparql?graph=http%3A//www.example.com/other/graph
>   http://www.example.com/david/sparql?graph=http%3A//www.example.com/other/graph
> 
> I guess part of what I'm saying is that this indirection is different,
> because it's dealing with a different problem.  It's not dealing with
> things being non-dereferenceable or whatever, it's dealing with the fact
> that SPARQL endpoints have the right to make Graph IRIs mean whatever
> they want, -- so they can only be understood/used by anyone else when
> they've been paired with the endpoints own URL.   Indirect
> identification does that pairing.
> 
>     -- Sandro
> 
> > Thanks,
> > James
> > 
> > [1] http://www.w3.org/TR/sparql11-http-rdf-update/#indirect-graph-identification
> > [2] http://www.w3.org/2011/09/LinkedData/ledp2011_submission_10.pdf
> > [3] http://tools.ietf.org/html/rfc5785
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> 
> 
> 
> 
Received on Tuesday, 29 November 2011 13:41:08 GMT

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