W3C home > Mailing lists > Public > public-rdf-wg@w3.org > April 2011

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

From: Dan Brickley <danbri@danbri.org>
Date: Mon, 18 Apr 2011 16:27:58 +0200
Message-ID: <BANLkTikXfmKUMdMViT5pr3T9FcSy+jhprA@mail.gmail.com>
To: nathan@webr3.org
Cc: Pat Hayes <phayes@ihmc.us>, Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>, Ivan Herman <ivan@w3.org>, RDF Working Group WG <public-rdf-wg@w3.org>
[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?).

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 14:28:33 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 16:25:41 GMT