On Tue, Nov 16, 2010 at 12:50 PM, Giovanni Bartolomeo
<giovanni.bartolomeo@uniroma2.it> wrote:
In order to speedly proceed toward closing some issues:
During the call we discussed two alternatives for identifying different personas, one is the currently adopted in PDX
http://wiki.oasis-open.org/xdi/PdxExample#Pattern.3ASubjectSuperset.28PersonaContext.29
and the second is the one I proposed here:
http://wiki.oasis-open.org/xdi/XdiOne/AddressingAndGraphModel#A.24has.24aforqualifyingcontexts
my problem with the first option is that it causes semantic conflicts with the mereological interpretation of structured identifier (see hereafter reported excerpt from minutes):
XDI adds a second feature to RDF, which is the ability of XRIs to express structured identifiers reflecting the merelogical structure of the graph, i.e., aggregation.
that's why I'm in favour of the second one. However, I've understood that the first pattern has been introduced for some issues related to the XRI resolution process - which I'm a bit less familiar with. Could you maybe guys provide some more details on this issue?
Giovanni, in preparation for today's call, let me explain that I don't think there is any conflict between the two patterns/models, i.e., that both work, and both are part of the way personas can/will be modeled in XDI.
Let me first summarize the two patterns. The first one (illustrated in your second link above), is where an individual, say =alice, can have different "personas" by being placed inside different supercontexts.
@company=alice
@sports.club=alice
This pattern can be even more granular using tagged supercontexts.
@company+salesperson=alice
@sports.club+pitcher=alice
Let me note that this concept of "persona" is most commonly referred to in directory systems as a "role", i.e., =alice has the +salesperson role at @company, and =alice has the +pitcher role at @sports.club.
The second pattern is where =alice defines her own subcontexts that represent different personas. This one is trickier, because =alice can have many subcontexts, and not all those subcontexts represent personas of =alice. For example:
=alice+tel ==> represents the collection of Alice's telephone numbers - not a persona of alice
=alice+friend ==> represents the collection of Alice's friends - not a persona of alice
So the question is, how can =alice define the set of personas for which she is the sole authority, not inside other authorities (like @company or @sports.club)?
The pattern for doing this (illustrated in your first link above) is the inheritance pattern, i.e., defining subcontexts of =alice that are by definition instances of =alice. Following the metagraph symbol proposal, this uses the superclass/subclass operator, !. It also uses the subject operator, $, to indicate that the subcontext is a new subject.
In this pattern (illustrated using i-names instead of i-numbers for readability), =alice can create subcontexts that semantically assert they are personas because they are each subclasses of =alice. Each of these personas is identified as a numbered subcontext, e.g., $1, $2, $3, etc.
The XDI statements that create these subcontexts are:
=alice/$1/$ ==> creates =alice$1
=alice/$2/$ ==> creates =alice$2
=alice/$3/$ ==> creates =alice$3
The XDI statements that asserts that these subcontexts are personas are:
=alice/!/=alice$1