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Subject: Re: [xdi] Minutes: XDI TC Telecon Thursday 1-2:30PM PT 2010-10-14

On Wed, Oct 20, 2010 at 7:27 AM, Giovanni Bartolomeo <giovanni.bartolomeo@uniroma2.it> wrote:

as from my AP of last week, here is a message about some concerns I have regarding the document


Please have a focus in the main picture labelled "New View". Let's assume there is a node which is the "root (context)", the next node is a "subcontext" and the addressing mechanism suggests to use the statement $/=drummond/$ to address drummond's context (where =drummond is a label associated to the ARC connecting the root to the first hierarchical subcontext, i.e. =drummond)

But issues arise when we need to describe a conventional triple, =drummond/+friend/=markus. In this case, we have three distinct labels, i.e. segments =drummond, +friend, =markus. Should all these be associated to arcs? If this is the case, then, is it correct to say that all labels are "predicates"? Actually they may represent predicates but also subjects or objects.

So, could you please clarify precisely how subject-predicate-object of a classical triple are represented in this new view of the graph?

In thinking about this, I realized that you and Andy discussed many years ago a similar idea in the ATI model (I was not member at that time but I've seen some presentations on the docbox), and also that I was inspired by this discussion in an earlier contribution


where labels are all associated to arcs - not to nodes. Except for the out-of-date semantics of some operators (which refers to an older version of the XDI RDF model documents), maybe is it a similar view that you are proposing?

Giovanni, I can't tell from your document (I haven't had enough time to read it), but yes, the fundamental idea of applying XDI to the RDF graph model was that all the XRIs describe arcs between nodes, and that the XRI (and also the URI when you add the URI base under the XRI 3.0 rules) of any RDF subject node was composed of any XRI path that led to that node.

So, in the graph below, the self-referential arc $ identifies the root node. From an RDF standpoint, this means that if this node is the subject of an RDF statement, the URI is http://xri.net/$. That is the global self-context, so it's use with any other global address is optional.


From the perspective of that root node, =a is a predicate to a subcontext. So that yields the XDI statement $/=a/$ and the RDF statement <http://xri.net/$> <http://xri.net/=a> <http://xri.net/$>.

Now that node =a is identified, it can be referenced in an RDF standpoint as a subject node. The XRI of that subject node is the address from the root -- =a -- and the URI is http://xri.net/=a .

So now we can say the following XDI statements: =a/+friend/=b, =a/+e/"foo", and =a/+c/(+d). In RDF this would be:

<http://xri.net/=a> <http://xri.net/+friend> <http://xri.net/=b>
<http://xri.net/=a> <http://xri.net/+e> <"foo">
<http://xri.net/=a> <http://xri.net/+c> <http://xri.net/(+d)>

Hope this helps, I look forward to discussing on today's call.


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