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Re: ISSUE-30: How does SPARQL's notion of RDF dataset relate our notion of multiple graphs?

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Mon, 18 Apr 2011 20:08:47 +0100
Message-ID: <4DAC8C3F.8020607@epimorphics.com>
To: public-rdf-wg@w3.org

Good example.

There are various ways the SPARQL dataset notion can be used.  IRI for 
each g-snap of the same g-box is certainly one of them.

The whole concept of RDF datasets was a recognition that quad usage 
existed.  "RDF dataset" is a compromise from various existing practices, 
from systems using the word "context" (usually collection of triples as 
subset of the graph) to multi-graph usages as you describe and 
variations in between.

On 18/04/11 15:27, Dan Brickley wrote:
> [snip]
> Let me offer a practical use case: the evolving RDF graphs served from
> FOAF and Dublin Core namespace URIs.
> For the FOAF case xmlns="http://xmlns.com/foaf/0.1/", the RDF
> available (via conneg, link rel or sometimes embedded in HTML) can be
> found in our Subversion server at
> http://svn.foaf-project.org/foaf/trunk/xmlns.com/htdocs/foaf/0.1/index.rdf
> ... you can fetch any version going back to ~2002 via public SVN.
> For the Dublin Core case, xmlns="http://purl.org/dc/elements/1.1/" and
> others nearby are documented in http://dublincore.org/schemas/rdfs/
> including links to each version of the schema file, and with
> social/process documentation of those changes at
> http://dublincore.org/usage/terms/history/
> Consider a SPARQL service devoted to keeping record of what key
> namespaces have said about themselves over the years. They could take
> each of these snapshot RDF files and put the corresponding triples in
> a different named graph. (Maybe we should prepare N-Quads/Trig dumps
> of the data for testing?).

and reserve the N-Quads and Trig as a syntax for RDF datasets.

If there is to be a syntax form for a different notion, then keep them 
apart (based on graph literals a la N3?).

> We should be able to queries such as "when did foaf:givenName change
> from Unstable status" or "when did DCMI begin to mention dc:audience
> ?". If we use the URI we 'GET'd for the graph name, these sort of
> historically minded queries won't be possible as the graphs will get
> mixed up.
> All this talk of HTTP response codes is great and nice and practical,
> ... so long as we're crystal clear that the Web gives back different
> things over time, and often we'll want to be explicit about that.
> Eventually we'll also want to be a bit more clear about security
> properties, such as which copies of a schema check out as having been
> signed by such-and-so key.
> cheers,
> Dan
> ps. for the foaf case, revisions are available via: svn log
> http://svn.foaf-project.org/foaf/trunk/xmlns.com/htdocs/foaf/0.1/index.rdf
> ...then you can pull them (per directory) eg. with:  svn co -r r186
> http://svn.foaf-project.org/foaf/trunk/xmlns.com/htdocs/foaf/0.1/ ...
> so you can see that
> <http://xmlns.com/foaf/0.1/homepage>
> <http://www.w3.org/2000/01/rdf-schema#domain>
> <http://xmlns.com/foaf/0.1/Person>  .
> ...used to be in there, before we broadened it. Question to my mind
> is, how do we elevate the tooling so you can find this out using
> SPARQL and RDF instead of SVN and grep?
Received on Monday, 18 April 2011 19:09:19 UTC

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