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Re: [PROPOSAL] Named graphs in RDFa

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Wed, 19 Dec 2007 16:00:45 +0000
Message-ID: <a707f8300712190800m91634bcj62a8d62d7d6d3cc3@mail.gmail.com>
To: "Hausenblas, Michael" <michael.hausenblas@joanneum.at>
Cc: public-rdf-in-xhtml-tf@w3.org, "SWD WG" <public-swd-wg@w3.org>

Hi Michael,

This is an interesting problem, and one I've avoided commenting on
because it could take every waking minute of the day. :) Anyway, all
of the following is in the 'theoretical' bin....

I think RDFa is unusual in that it doesn't have a named graph problem
in the way that, say, RDF/XML does, because the XHTML document *is*
the 'named graph'.

The interesting thing about an HTML/XHTML document is that there is
both a head and a body section of the document, which means that we
could define things in such a way that we are making *two* lots of
statements; one lot about the document itself, and one lot about the
'content' referred to by the document.

The document itself is a named graph, since it has a URL, and contains
metadata. Of course, normally all metadata in the document is 'about'
that document unless overridden by an @about, so to distinguish
between statements about the document (i.e., the graph) and statements
about some other things you'd always have to add an @about.

However, if a typical document looked like this:

  <html>
    <head about="">
      ...statements about the named graph...
    </head>
    <body about="#">
      ...statements about the content, e.g., my FOAF page...
    </body>
  </html>

you would effectively have a 'named graph', which is the information
resource at "", accompanied by a resource, identified by "#"; note how
this might also solve the interminable information resource question.

(As it happens this trick of distinguishing between the document
carrying the metadata and what the metadata is about could have been
done with RDF/XML, but in RDF/XML if @rdf:about is empty it means that
statements are being made about the current document; in short, there
is no way to distinguish between the document that contains the graph,
and the graph itself.

If we also added a statement that the 'primary topic' of the named
graph, was the resource identified in the body:

  <html>
    <head about="">
      <link rel="foaf:primaryTopic" href="#" />
      ...statements about the named graph...
    </head>
    <body about="#">
      ...statements about the content, e.g., my FOAF page...
    </body>
  </html>

then everything is complete; now, when someone links to the 'graph'
from an HTML page (the most likely scenario), it is a simple matter to
sort out what exactly is being referred to.

Regards,

Mark

On 19/12/2007, Hausenblas, Michael <michael.hausenblas@joanneum.at> wrote:
>
>
> All,
>
> Proposal:
> Add a mechanism to RDFa that allows to indicate
> a graph's provenance (aka named graphs, etc.).
>
> In the first phase we should decide IF we want
> this (or not :), then if/when we agree, we should
> discuss HOW to implement it.
>
> Rational:
> Due to the ongoing discussions [1] and Fabien's
> W3C member submission [2] is ask myself:
> Why don't we introduce this feature in RDFa?
>
> As we are about (or partly already did) add new
> stuff anyway (such as XHTML voc, CURIE, etc.),
> why not supporting this IMO very important feature
> right from the beginning?
>
> Any thoughts?
>
> Cheers,
>         Michael
>
> [1] http://lists.w3.org/Archives/Public/semantic-web/2007Dec/0035.html
> [2] http://www.w3.org/Submission/rdfsource/
>
> ----------------------------------------------------------
>  Michael Hausenblas, MSc.
>  Institute of Information Systems & Information Management
>  JOANNEUM RESEARCH Forschungsgesellschaft mbH
>  Steyrergasse 17, A-8010 Graz, AUSTRIA
>
>  <office>
>     phone: +43-316-876-1193 (fax:-1191)
>    e-mail: michael.hausenblas@joanneum.at
>       web: http://www.joanneum.at/iis/
>
>  <private>
>    mobile: +43-660-7621761
>       web: http://www.sw-app.org/
> ----------------------------------------------------------
>
>


-- 
  Mark Birbeck, formsPlayer

  mark.birbeck@formsPlayer.com | +44 (0) 20 7689 9232
  http://www.formsPlayer.com | http://internet-apps.blogspot.com

  standards. innovation.
Received on Wednesday, 19 December 2007 16:00:54 GMT

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