Minutes: XDI TC Telecon Thursday 1-2:30PM PT 2011-01-20

[Drummond Reed <drummond.reed@xdi.org>]

Following are the minutes of the unofficial telecon of the XDI TC at:

Date:  Thursday, 20 January 2011 USA
Time:  1:00PM - 2:30PM Pacific Time (21:00-22:30 UTC)

ATTENDING

Markus Sabadello
Giovanni Bartolomeo
Drummond Reed
Michael Schwartz
Joseph Boyle

GUEST
Jay Glasgow


THE GOTOMEETING FOR TODAY IS:
     https://www2.gotomeeting.com/join/969244355

THE IDEARPAD LINK FOR TODAY IS:
     http://xdi.idearpad.org/19


1) REVIEW GIOVANNI BARTOLOMEO'S PDF NOTES ON THE GLOBAL GRAPH

We discussed Giovanni's document at:

   http://www.oasis-open.org/committees/download.php/40757/notes%20on%20the%20global%20graph.pdf

Giovanni first explained that one purpose of this document is to
explain the differences in XDI and RDF graphs, and to show where the
two of them fit together. It starts by showing that relational and
literal arcs are identical in both; the difference is the contextual
arcs, which only exist in XDI graphs.

XDI synonyms are established by having multiple contextual arcs
pointing to the same node. This is illustrated in the third graph,
where the final node is identified by both a single arc from the root
and from another arc from a child of the root.

Giovanni's paper also shows how an XDI graph  can express "same
identity different context", which we know from a  paper at the W3C
RDF Workshop is an issue in RDF, because it does not  have an explicit
facility for expressing context.

Another capability illustrated in the document that is unique to XDI
graphs is the ability to identify properties in the context of a
specific subject, and make statements about those properties in that
context. Giovanni said that this is currently an active topic within
the Linked Data community.

Another pattern shows how to associate metadata on a property within a
context by expressing that property as a subcontext. And example is
the property +friend within the context =abc. For purposes of
describing this property, this becomes =abc+friend. This has subtle
differences from the "property on a property" semantics that Drummond
proposed on our last call before the holiday break. However Drummond
now agrees that this pattern looks like the best one for the uses
cases Giovanni's document discusses.

Giovanni proposed that this same approach can be extended to the the
objects of a relational property, i.e., if you want to talk about the
object of the XDI statement =abc/+friend/=xyz, that subject can be
identified in that context by the address =abc+friend=xyz.

Drummond pointed out that the fact that this shows that =xyz can be
correlated between both contexts -- global (where it is just =xyz),
and the =abc+friend context, where it is =abc+friend=xyz. He agreed
with Giovanni that this is not something RDF and Linked Data appears
to be able to handle today.

# GIOVANNI will upload a revised copy of the document with the one
erroneous graph fixed and with revisions to the final graphs about
multi-valued properties.

# DRUMMOND will upload a revised set of graphs showing the patterns on
which his example dictionary is based.

We will discuss these two documents on next Thursday's call.


2) MIKE SCHWARTZ USE CASES

We did not have time to discuss Part 2 of MIke's use cases for Poken
friend requests across LDAP boundaries, but see the next item.


3) CALL FREQUENCY

We discussed the potential for a second call focused on
implementation, so we can make sure that each week we have time for
calls on both semantics and implementation. Mike volunteered 10AM PT
on Fridays.

# DRUMMOND will send an email to the list proposing a second telecon
on implementation at 10AM PT on Fridays.


4) NEXT CALL

The next semantics call will be next week at the regular time. The
next implementation call will be Friday January 28 at 10AM PT.



------------
ONGOING ISSUES LIST

Each of these is a candidate for the agenda for future calls.

* PROPOSED CONSTRUCTS/OPERATORS FOR XDI

Discuss the following wiki page originally posted by Giovanni:

  http://wiki.oasis-open.org/xdi/XdiNewFoundation

* DICTIONARY STRUCTURE

Mike would like an example of the PDX dictionary as soon as we can do it.

*   EQUIVALENCE SEMANTICS

Close on whether we need an additional $ word that is the equivalent
of Higgins Personal Data Model (PDM)  semantics   of h:correlation,
which is not as strong as $is.

      http://lists.oasis-open.org/archives/xdi/201006/msg00036.html

* COOL URIS

Continue previous discussion about the use of standard RDF URIs in XDI:

  http://lists.oasis-open.org/archives/xdi/201006/msg00023.html