Minutes: XDI TC Telecon Thursday 1-2PM PT 2009-06-18

["Drummond Reed" <drummond.reed@cordance.net>]

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

Date:  Thursday, 18 June 2009 USA
Time:  1:00PM - 2:00PM Pacific Time (20:00-21:00 UTC)

ATTENDING

Bill Barnhill 
Markus Sabadello 
Drummond Reed

REGRETS

Giovanni Bartolomeo


1) UPDATES

We provided some general updates since it had been a month from the last
call. 

Drummond and Markus explained the XDI-related work they have been doing with
Mydex, a new Community Interest Corporation in the U.K. focused on VRM
(Vendor Relationship Management). They have also been exploring an XDI
messaging application.

Bill said he has been working on an activity stream application. 


2) $HAS INFERRENCE

Based on our conclusions in May regarding the $has metagraph predicate
definition, Drummond wanted to confirm for the updated spec text that
+x/$has/+y (and its inverse +y/$is$has/+x) infers exactly four XDI RDF
statements:

	(+x/+y)
	+x+y
	+x+y/$is$a/+y
	+y/$a/+x+y

We agreed this was the case. It can be easier to parse using a real-world
example, such as:

	=bill/$has/+ball

This infers four XDI RDF statements:

	(=bill/+ball)
	=bill+ball
	=bill+ball/$is$a/+ball
	+ball/$a/=bill+ball

Bill pointed out that the N3 abbreviation for rdf:type (subClassOf) is just
"a". Thus in N3 you would write:

	:Bill a :Person

Whereas in XDI RDF we use the property $is$a for subClassOf, and the inverse
- $a - for superclass. So we would write:

	=bill/$is$a/+person
	+person/$a/=bill

So it is a bit confusing that our $a has the inverse semantics of the N3
"a". Unfortunately this can't be avoided for two reasons:

	1) $a is our metagraph predicate for incoming arc relationships,
which is the inherent basis for typing.
	2) $is$a reads the same as English for expressing subClassOf
relationships, e.g., =bill/$is$a/+person.

So it was just an unfortunate choice that N3 choose "a" instead of "is-a" to
represent subClassOf relationships.

Bill also pointed out that full N3 does not directly translate into
conventional RDF because it is a superset of RDF. It includes formula,
variables, logical implications, and functional predicates, as well as
providing a textual syntax alternative to RDF XML. In this way XDI RDF seems
much closer to N3 than to conventional RDF.


3) NEW BUSINESS

We discussed that if XRI Resolution 3.0 is defined abstractly with multiple
bindings, XDI is one possible binding. We need to keep this in mind as the
XRI TC finishes the XRI 3.0 spec suite.


4) NEXT CALL

Due to travel and other conflicts, we will NOT hold a call next week, but
will reconvene in two weeks, on Thursday, July 2.