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Re: Well Behaved RDF - Taming Blank Nodes, etc.

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Wed, 12 Dec 2012 21:35:16 +0100
Cc: Pat Hayes <phayes@ihmc.us>, semantic-web <semantic-web@w3.org>
Message-Id: <8F268190-A3EC-4074-9211-698C0E21ADA7@inf.unibz.it>
To: David Booth <david@dbooth.org>

On 12 Dec 2012, at 20:09, David Booth <david@dbooth.org> wrote:

> But according to
> http://web.ing.puc.cl/~marenas/publications/iswc11.pdf
> the vast majority of RDF documents (over 98% of their samples) use blank
> nodes in non-problematic ways.  (I.e., they contain no blank node
> cycles, and thus do not cause the graph isomorphism complexity problem.)
> At present the many applications that process RDF have to pay for the
> sins of those (very) few RDF graphs that use blank nodes in problematic
> ways.
> Actually, it would be interesting to examine whether those <2% of graphs
> that did have blank node cycles really needed them.  My suspicion is
> that the authors could have simply minted a few URIs to break those
> blank node cycles and turn them into non-problematic blank node trees.
> In the nearly 4 million RDF documents Mallea, Arenas, Hogan, and
> Polleres examined, the maximum blank node treewidth they found was 7,
> which I think (though a graph theory expert would have to confirm) that
> only 6 URIs would have to have been minted to turn it into a tree.

My suspicion (also compatible with the experimental data) is that people are using RDF to na´vely implement an "object model". I believe that RDF is not used in its full power simply because people are not used to model directly with a relation-based language, where bnode-cycles would be more natural.
Is this good? Probably not, since if we actually need an object model then we could go back to Corba :-) [just kidding].
Technically speaking, the idea to simplify RDF by disallowing bnode-cycles is appealing.

Received on Wednesday, 12 December 2012 20:35:51 UTC

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