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Subject: RE: [xdi] XDI contexts and cross-references
Good point, Markus – since I only
had one XDI subject in these examples, the cross-reference example was relative
to that XDI subject. But yes, absolutely, cross-references can be either
relative or absolute. To illustrate, here’s an XDI
document with three subjects that uses absolute cross-references across the
subjects. It also shows a way to more deeply contextualize data context,
because now the actual literal email addresses for =drummond are in separate XDI
subjects that represent contextualize personas of =drummond (in this case home
and work). =drummond +email / =drummond+home +email =drummond+work +email +email+home (=drummond+home/+email) +email+work (=drummond+work/+email) +email$ (=drummond+work/+email) =drummond+home +email “dsr.example@gmail.com” =drummond+work +email “drummond.example@cordance.net” =Drummond From:
markus.sabadello@gmail.com [mailto:markus.sabadello@gmail.com] On Behalf Of Markus Sabadello
On Fri, Mar 28, 2008 at 8:25 AM, Drummond Reed <drummond.reed@cordance.net>
wrote: Another question that came up on today's call involved the
meaning of the following statement (a simplified version of the example we were
discussing from the XDI RDF Model doc, http://wiki.oasis-open.org/xdi/XdiRdfModel):
=drummond/+email//=drummond/+email+home Does that mean that =drummond/+email is an equivalent XDI
statement to =drummond/+email+home? No, it only means that the statement =drummond/+email is the
parent context for the statement =drummond/+email+home. =drummond/+email could
also be the parent context for the statement =drummond/+email+work. In X3
Simple, this would graph as: =drummond +email
/
=drummond
+email+home
+email+work So if you did an XDI $get on =drummond/+email, the response
would be the entire graph above. That graph in turn could be part of this
larger graph: =drummond +email
/
=drummond
+email+home
+email+work +email+home +email+work
"drummond.example@cordance.net" +email$
(/+email+work) This larger graph includes the cross-reference
"(/+email+work)". This reads as, "relative to the same XDI
subject, refer to the +email+work predicate". Unlike a subcontext, this
statement IS saying that one XDI statement refers directly to another one,
i.e., the first XDI statement below refers to the second one: =drummond/+email$/(/+email+work) =drummond/+email+work So, for purposes of illustration of these two concepts –
XDI contexts and XDI cross-references, an XDI request/response pattern against
the full graph above, translated from English into X3, might be: Q: "Markus would like Drummond's email address." =markus $get
/
=drummond
+email A: "Drummond has two email addresses, home and work." =drummond +email
/
=drummond
+email+home
+email+work Q: "Then Markus would like Drummond's home email
address." =markus $get
/
=drummond
+email+home A: "Here is the value." =drummond +email+home ************* A different request response pattern against the same path might
be: Q: "Markus would like Drummond's canonical email
address." =markus $get
/
=drummond
+email$ A: "Drummond's canonical email address is his work email
address." =drummond +email$
(/+email+work) Q: "Then Markus would like Drummond's work email
address." =markus $get
/
=drummond
+email+work A: "Here is the value." =drummond +email+work
"drummond.example@cordance.net" *********** Note that one of the last two roundtrips could be eliminated by
the simple rule that the server would resolve xrefs within the same XDI
context. This would result in the following request/response: Q: "Markus would like Drummond's canonical email
address." =markus $get
/
=drummond
+email$ A: "Drummond's canonical email address is his work email
address, and here is the value." =drummond +email$
(/+email+work) +email+work
"drummond.example@cordance.net" |
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