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Subject: More comments on XDI metagraph predicate examples (was: RE: [xdi] Minutes: XDI TC Telecon Thursday 1-2PM PT 2008-12-18)
At 09.09 30/12/2008, Drummond Reed wrote:
Giovanni pointed out that Statement 6 in the xdi-rdf-graphing-v1 document is
not consistent with the link contract example found on page 33 of the
xdi-rdf-model-v11 document:
http://www.oasis-open.org/committees/download.php/29748/xdi-rdf-model-v11.pd
f
In that document, =drummond/$has/+friend$contract results in the XRI
=drummond+friend$contract, but it should be =drummond(+friend$contract).
Drummond agreed this should be changed in the next version.
UPDATE: In his study of the Statement 6 issue identified by Markus, Drummond
subsequently revised the proposed graph structure for compound $has
statements. This eliminates the issue identified by Markus and also removes
the inconsistency with the V11 XDI RDF Model document. V2 of the XDI RDF
Graphing document has been posted at:
[giovanni] To further clarify, I also propose to have
(1) =drummond+friend/$has/$contract
instead of
(2) =drummond/$has/+friend$contract
even if they both result in
(3) =drummond+friend$contract
statement (2) seems to me to assert that a subject +friend$contract exists regardless the context it is intended to be into (=drummond). Statement (1) instead put $contract in the context of =drummond+friend and +friend in the context of =drummond. Or maybe I'm missing something?
[=Drummond] No, I think you are correct, statement (2) implies that there is a XDI subject with the XRI +friend$contract. But I think that is implied in all cumulative $has statements. As I clarified in the page I just posted ( http://wiki.oasis-open.org/xdi/XdiOne/RdfGraphModel), in an XDI context, the XRI =drummond+friend$contract infers all of the following XDI RDF statements:
(a) =drummond/$has/+friend/
(b) =drummond+friend/$has/$contract
(c) =drummond/$has/+friend$contract
+a/$has/+b+c ==> +a+b+c +a+b/$has/+c ==> +a+b+chowever, if you want to REVERSE these statements, starting from +a+b+c, you can infer EITHER (1) +a/$has/+b+c OR (2) +a+b/$has/+c OR (3) both. And the outcomes are different in the three different cases.
[giovanni] In example #8 (equivalence +x/$is/+y) the arc connecting the two circles is labelled with +y, does it have a particular meaning? Maybe, for consistency's sake, it is better to maintain the graphical convention to name the arc after the predicate. Since $is is a symmetric predicate, what do you think about the following amendment?
[=Drummond] The graph you draw is 100% accurate – it is a depiction of the full metagraph statement, i.e., of the XDI RDF statement +x/$is/+y. The graph I was drawing is a depiction of the resulting statement in the XDI RDF graph, which is that the node +x has a self-referential arc of type +y. So both are correct, and I agree we should show both in the two columns. I’ll make a note to revise that in the next version.
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