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statements about a graph (Named Graphs, reification)

From: K-fe bom <u9x3n_15so@hotmail.com>
Date: Mon, 03 Sep 2007 14:31:51 +0000
Message-ID: <BAY114-F38EBF4C0177AF620FF0550E1C90@phx.gbl>
To: semantic-web@w3.org


Greetings,
I'm looking for the best way to model certain statements about statements. I 
find that Named Graphs are part of what I need, since I was really looking 
for a way to refer to a whole set of RDF statements as a unit.
   More specifically I'm looking for comments and examples of how to make 
statements about a Named Graph, ideally all living in a RDFa document.
  If you assume there is some Named Graph somewhere with a URI, I want to 
make some RDF statements about this one Named Graph as if annotating the 
Named Graph. Call it metastatements if you will.
  I was actually surprised that RDF didn't embbed that capability directly 
in its syntax and semantics. I had the first impression that reification 
would provide that, but when I took a closer look (the conventional way of) 
reification was not referring to graphs as a whole.
  As for the conventional way of reification, I see some problems trying to 
apply it here. I can't find examples of what that would look like, but I can 
speculate. The reification statements would refer to the graph and break the 
graph apart. Trying still to stick to the so called "conventional way of 
reification", the reification statements would affirm the named graph is a 
named graph and would explode the graph into statements. Well, that isn't 
useful to me. I was hoping to annotate the graph.
  If I try to summarize the alternatives I list:
1 - To mix the (meta)statements with the original information. This would be 
similar to the example given in the Reification section of [1] that 
attributes a creator to one triplet. I'm reluctant to go with this option 
because there seems to be no separation between statements and 
metastatements.
  2 - Not to use reification. I would refer to the Named Graph and make 
statements about the graph. This seems to be the best option so far to me. 
It's just that in a way this looks similar to alternative 1 to me.
  3 - To use reification in a non-conventional way.

What confuses me is that reification first sounded as providing the 
semantics to make 'statements about statements'. But if I use reification in 
a non-conventional way I would be going against the current and providing 
some 'proprietary' semantics that perhaps would compromise interoperability 
between applications. In the same token by not using reification altogether 
it seems that I would be 'making statements about statements' mixing layers 
of abstraction in a model.

  I'm not so interested in discussing the semantics of reification for the 
sake of it. I'm more interested in hearing suggestions for the best approach 
to model the data. So what are your thoughts? How would one go about 
annotating a named graph (in RDFa ideally)?


Kind regards,
Gustavo Frederico


[1] http://www.w3.org/TR/rdf-primer/#reification
Received on Monday, 3 September 2007 14:32:10 UTC

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