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

On Dec 12, 2012, at 11:09 AM, David Booth wrote:

> On Wed, 2012-12-12 at 09:43 -0800, Pat Hayes wrote:
>> On Dec 12, 2012, at 9:01 AM, David Booth wrote:
> [ . . . ]
>>> A Well-Behaved RDF graph is an RDF graph that can be serialized 
>>> as Turtle without the use of explicit blank node identifiers. 
>>> I.e., only blank nodes that are implicitly created by the 
>>> bracket "[ ... ]" or list "( ... )" notations are permitted. 
>> That is too restrictive. There is a real need to be able to describe
>> things such as "Joe's father" or "a woman in a red dress" which are
>> naturally phrased as bnodes with identifying descriptors attached to
>> them. 
> Perhaps, for some RDF authors.  And those authors could use full RDF
> instead of the Well Behaved RDF profile.  But according to
> 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.)

I also don't want any cycles, but that is much weaker than your proposal. Why not just say that wellbehaved means, no bnode cycles?


> 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.
> -- 
> David Booth, Ph.D.
> Opinions expressed herein are those of the author and do not necessarily
> reflect those of his employer.

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Received on Thursday, 13 December 2012 07:08:20 UTC