Re: [xdi] Thoughts in Modeling Personas in XDI

On Tue, Nov 23, 2010 at 4:50 PM, Giovanni Bartolomeo <giovanni.bartolomeo@uniroma2.it> wrote:

* * * IMPORTANT for XDI graph model specs: TC MEMBERS PLEASE READ * * *

Hello Drummond,

still thinking at a possible solution according to our findings of last week's call (http://lists.oasis-open.org/archives/xdi/201011/msg00023.html), I was asking myself some very basic questions.

You said

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+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.

Now, what is unclear to me is why these two patterns differ one from another. Could we figure out any use case showing that a persona (second pattern) cannot be thought at as a role of an individual in an organization or group of members (first pattern)? I mean, from my PoV, +work, +baseball, +home, etc. are all "contexts" in which =alice does play a "role": she is an employer in her "work context", a player in her "baseball (team) context" and a housewife in her "home context".

Furthermore, to be precise, +work, +baseball, +home, are not proper instances of contexts, rather they are different "categories" of contexts; e.g. =alice is a +driver in @example.bus.company, not in +work; she is a +player in @example.baseball.team, not in +baseball, she is +wife in @example.family, not in +home, etc. Finally she is herself in her default context, which is, simply, =alice.

A third thought is about the usage of "numbered subcontext": $1 ("the first", $2 ("the second"), $3 ("the third"), ... and $ (understood as "all of them") itself are OK when applied to an identifier which is, by itself, a group - I would say an array - i.e. an entity that naturally does contain members: =alice+sister$1, @example.baseball.team+player$2, @example.bus.company+driver$, @example.family+member$, etc. However, this is less convincing when applied to identifiers identifying entities which are - per se - unique, such as =alice.

In other words, we should not have multiple =alice, rather we should probably aim at having the very same =alice playing, as you said, different roles in different contexts - or better - context instances.

I might miss some important points here. If this is the case, please let me know - the ideal would be to have a use case for this - If not, then I think that this proposal is so simply that it could even succeed.. maybe.

Best Regards,
Giovanni

Def. Quota "Drummond Reed" <drummond.reed@xdi.org>:

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
=alice/!/=alice$2
=alice/!/=alice$3

Thus the semantics of =alice$[digits] where [digit] is a placeholder for any
number of digits is that it represents a persona of =alice defined by
=alice.

This doesn't yet answer the question of how =alice can identicate what type
of personas these represent, i.e., which one is her +home persona, her +work
persona, etc. These can be done with other XDI statements:

=alice/+home/=alice$1
=alice/+work/=alice$2
=alice/+baseball/=alice$3

Talk to you shortly,

=Drummond

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