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Re: namedNode? in predicate position?

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 4 Sep 2001 12:13:42 -0700
Message-Id: <v04210103b7bad6c376b1@[130.107.66.237]>
To: Aaron Swartz <aswartz@upclink.com>
Cc: w3c-rdfcore-wg@w3.org
>On Wednesday, August 29, 2001, at 09:27  AM, Dave Beckett wrote:
>
>>>while at next telecon agenda items,
>>>what about the N-triples/MT related questions
>>>1. predicate ::= uriref  versus predicate ::= uriref | namedNode?
>>
>>Does RDF allow, let's call it, non-URI-ref for predicates?
>>I don't think so, at present.  In the graph model in the original
>>M&S, predicates are arrows with URIs, they are never empty circles.
>
>Well maybe it's an arrow without a URI.

The problem would be having the, er, 'same' arrow linking A to B and 
also C to D:

A _:xxx B
C _:xxx D

The chief utility of the graph syntax is that it gets rid of the 
problems that arise from having to provide several distinct 
renderings of a single anonymous node, since anonymous nodes are 
unique in the graph, ie they only occur once (contrast <anonNodes> in 
Ntriples). If we have to include an anonymous arrow in the graph in 
two places but indicate that they are the 'same' by giving them a 
special anonymous label, then the confusion is back in the graphs in 
spades. In fact there would then be no particular advantage to the 
RDF graphs over Ntriples documents, and we would have to go back to 
some notion of quantifier scoping in the model theory. Which we could 
do, but please lets us get this matter settled one way or the other.

>I think that princeNodes should be allowed in the predicate slot... 
>they're rather useful.
>
>While I'm giving unsolicited advice, I think that a DLG is probably 
>not the best way to represent the RDF model... it's sort of 
>difficult to picture arrows pointing at other arrows.

If *that* is allowed then the M&S is totally screwed up. Is it legal 
RDF to have a property be the value of another property??

Pat

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Received on Tuesday, 4 September 2001 15:12:26 EDT

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