W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > June 2003

Re: blank nodes out the wazoo

From: pat hayes <phayes@ihmc.us>
Date: Tue, 10 Jun 2003 11:25:42 -0500
Message-Id: <p05210604bb0bb68e9533@[10.0.100.24]>
To: Graham Klyne <gk@ninebynine.org>
Cc: w3c-rdfcore-wg@w3.org

>At 16:42 09/06/03 -0500, pat hayes wrote:
>>While fixing a silly mistake in the MT document, I noticed the 
>>following. We require that RDF graphs contain no redundancies in 
>>the sense that the same triple cannot occur more than once in the 
>>graph. However, they can contain redundancies in the sense that a 
>>triple with a bnode in it can be duplicated with a different bnode, 
>>even though the resulting triples would look the same in a graph 
>>diagram. The resulting graph has no extra information in it, but 
>>this quirk allows an RDF graph to have infinitely many 
>>consequences. For example, a single triple
>>
>>a p b .
>>
>>has infinitely many consequences;
>>
>>_:x p b .
>>a p _:y .
>>_:z1 p _:z2 .
>>_:z3 p _:z4 .
>>-:z5 p _:z6 .
>>....
>>
>>where all these bnodes are distinct; see attached jpeg.
>>
>>My question is, does the WG feel that it might be worth ruling this 
>>out as a syntactic possibility? If this kind of bnode-duplication 
>>were ruled out, then the set of graphs simply entailed by any RDF 
>>graph would be finite.  That would generalize the 
>>no-duplicate-triples condition implicit in our definition of a 
>>graph as a set, to treat triples which 'look' the same when you 
>>erase the bnode labels as though they literally were the same.
>
>From an implementation perspective, I'd be concerned about ruling 
>out redundant bnode triples as syntactically disallowed.  I think 
>this would make the implementation of merging two 
>syntactically-valid graphs very much more difficult (but not 
>impossible).

Yes. and after sleeping on it, I think its best not to tinker with 
the syntax at this stage in any case. And I am pretty sure that I can 
handle the problem without doing anything so drastic.

So, Never Mind.

Pat
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Received on Tuesday, 10 June 2003 12:25:56 EDT

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