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Re: Reification - whats best practice?

From: Lars Marius Garshol <larsga@ontopia.net>
Date: Thu, 26 Aug 2004 10:38:40 +0200
To: "'RDF interesting groupe'" <www-rdf-interest@w3.org>
Message-ID: <m3oekycmzz.fsf@pavarotti.intern.opera.no>


* Sandro Hawke
| 
| While I'm fond of quad stores (eg in cwm and SWI prolog) and agree
| they're generally the way to go -- 

I find this discussion really interesting, because my conclusion from
studying the possible integration of topic maps and RDF for a long
time is that if RDF were quads instead of triples the integration
would be an awful lot easier.

There are three main sticking points to TM/RDF integration[1]:

  - representing scope in RDF, (requires reification if you use
    triples),

  - the fact that reification is so awkward in RDF, and

  - the representation of associations.

Quads solve the first two, and the second one can then be worked
around by making the association a blank node. It's imperfect, since
it's not symmetric with RDF, but workable.

For the Reference Model workshop that the ISO committee had a couple
of weeks ago in Montréal I wrote up a rough sketch of this:
<URL: http://www.ontopia.net/topicmaps/materials/quads-montreal-2004.pdf >

It's not fully worked out, and there are problems with it that aren't
mentioned in the slides (because I hadn't thought of them at the
time), but it seems quite promising.

| how do you propose exchanging quad-store data?  My store knows that
| source x said {a b c}, but how do I publish that fact?

Well, leaving RDF/XML aside, it doesn't seem very difficult to create
an XML syntax where the reification is done without having to create
global identifiers for the statements. For example:

  <bogus-quad-syntax>
    <statement subject="a" property="b" object="c">
      <statement property="source" object="x"/> 
      <!-- subject is implicitly parent statement -->
    </statement>
  </bogus-quad-syntax>
 
[1] More detail than you are likely to want can be found in my paper
on this: <URL: http://www.ontopia.net/topicmaps/materials/tmrdf.html >

-- 
Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
GSM: +47 98 21 55 50                  <URL: http://www.garshol.priv.no >
Received on Thursday, 26 August 2004 08:39:13 UTC

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