Minutes: XDI TC Telecon Thursday 1-2PM PT 2009-03-26

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

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

Date:  Thursday, 26 March 2009 USA
Time:  1:00PM - 2:00PM Pacific Time (21:00-22:00 UTC)

ATTENDING

Markus Sabadello
Nick Nicholas
Drummond Reed
John Bradley
Bill Barnhill

REGRETS

Giovanni Bartolomeo


1) CONTINUE $HAS AND +X/+Y/+X+Y DISCUSSIONS

See the minutes of the last two meetings at:

	[1] http://lists.oasis-open.org/archives/xdi/200903/msg00005.html 
	[2] http://lists.oasis-open.org/archives/xdi/200903/msg00018.html

Also the posts at:

	[2] http://lists.oasis-open.org/archives/xdi/200903/msg00004.html
	[3] http://lists.oasis-open.org/archives/xdi/200903/msg00006.html
	[4] http://lists.oasis-open.org/archives/xdi/200903/msg00007.html
	[5] http://lists.oasis-open.org/archives/xdi/200903/msg00008.html

The main page we discussed on this call was the new XDI Metamodel page:

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

We began by discussing the proposition brought up last week, i.e., that the
$has predicate emight be a generalization of all predicates (all arcs). Bill
explored this by explaining all the pairings he derives from
=abraham/+son/=isaac (@=, =abraham), (+metadata+described, =abraham),
(=abraham, =abraham+son), (+son, =abraham+son). He said they are in the form
(group-id, member-id).

Drummond explained that he felt strongly that $has was not the
generalization of all predicates, but in fact that it had very specialized
purpose and semantics vs. $has$a. For example, =abraham+son infers the
metagraph statement =abraham/$has/+son. This also asserts a cardinality of
exactly one +son outgoing arc from =abraham that has an object =abraham+son.

In addition it infers that:

	a) =abraham/$has$a/+son, but does NOT infer any cardinality of the
number of sons.
	b) =abraham+son/$is$a/+son, but does NOT infer any instances of
sons.

We then compared RDF and XDI RDF statements. Bill gave the example:

	foaf:Person has a property ex:son
	Abraham is a instance of foaf:Person
	Abraham has a property of ex:son

Those same statements in XDI RDF (roughly):

	+person/$has$a/+son
	=abraham/$is$a/+person
	=abraham/$has$a/+son

Drummond pointed out that the last statement means =abraham/+son, not
=abraham+son. The latter would be the metagraph statement
=abraham/$has/+son.

Bill said that in term of his groupID, memberID pairs, this would be
+person=abraham, =abraham+son.

Drummond gave the same example in English of "Boeing has a airplane called
[list of airplane objects here]" and "Boeing airplanes" as a noun.


Bill said, "So you're saying @boeing+plane(xx) => (xx) is a class, and
@boeing/+plane/(xx) => (xx) is an instance? Drummond agreed.

Nick noted that there is a confusion between $has at the graph and metagraph
level, and also that we need to discuss arcs between two individuals (vs.
arcs from a class to an individual). 

# DRUMMOND to make that a topic for next weeks call.

Bill also noted the following link to a good series of posts on A-Box vs
T-Box:

	http://www.mkbergman.com/?p=471

And also that for the next call, one method of whiteboarding is to use the
Coccinella client:

	http://thecoccinella.org/download


2) NEXT CALL

Regular time, 1-2PM PT (20:00-21:00 UTC).