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Subject: Re: [xdi] Minutes: XDI TC Telecon Thursday 1-2PM PT 2010-01-07
Dear Drummond,
In order to be very clear, could you please distinguish between proposals and agreements? Some suggested changes to your notes are below.
Kind Regards,
Giovanni
1) $HAS ASSOCIATIVITYhttp://lists.oasis-open.org/archives/xdi/201001/msg00011.html<http://www.oasis-open.org/committees/download.php/35421/xdi-rdf-box-graphs-v1.pdf>
See the thread started by Giovanni at:
For the sake of completeness, please check also the following of this thread:
http://lists.oasis-open.org/archives/xdi/201001/msg00014.html
http://lists.oasis-open.org/archives/xdi/201001/msg00019.html
http://lists.oasis-open.org/archives/xdi/201001/msg00022.htmlPlease note that during the conference we DID NOT AGREE on this concept. Current specs (http://wiki.oasis-open.org/xdi/XdiOne/RdfGraphModel) says:
We began discussion by revisiting some of the decisions we made about the
$has operator last spring.
# ACTION: Drummond will look for an email or minutes that he sent last
spring about deciding that $has$a still had a role.
We then progressed into talking about the nature of $has relationships, and
Drummond's assertion that from an RDF standpoint, a $has statement does not
actually assert that an RDF graph node has an outgoing RDF graph arc. That's
the job of a $has$a statement, and the reason that only $has$a statements,
and not $has statements, can have cardinality.
So what Drummond explained is that $has statements do not assert that the
$has object is an outgoing arc from the $has subject, only that the $has
object is a valid outgoing arc for the $has subject. The reification of the
relationship between the $has subject and the $has object, for example
reifying +a/$has/+b into (+a/+b), creates a new XDI RDF subject +a+b.
"$has describes the relationship between a node and an outgoing arc in the XDI RDF graph. The subject of a $has statement is the XRI of the node from which the arc originates, and the object is the XRI of the arc."
Bill pointed out that +a/$has/+b implies +a/+b and viceversa, i.e. they are logically equivalent statements.
Please note that during the conference we DID NOT AGREE on any notion of "containment" above suggested.
This led us into a discussion of the relationship of XDI RDF graphs and
conventional RDF graphs. For example, the XDI statement +a/$has/+b diagrams
as a normal subject/predicate/object triple in an XDI RDF graph. But when
you convert that statement into what it describes in a conventional RDF
graph, it translates into a single RDF subject node identifier, +a+b. This RDF node "contains" the XDI RDF graph +a/$has/+b, but that is transparent to
conventional RDF, because conventional RDF does not have the notion of
contexts, i.e., graphs as objects of other graphs.
What we agreed during last Spring (reported in http://lists.oasis-open.org/archives/xdi/200904/msg00021.html):
#1: +x/$has/+y INFERS:
+y/$is$has/+x
+x+y/$is$a/+y
+y/$a/+x+y
+x+y
+x/+y
The corollary is also true, i.e.:
#1A: +x+y INFERS
+x/$has/+y
+y/$is$has/+x
+x+y/$is$a/+y
+y/$a/+x+y
+x/+y
+x/$has/+y ==> (+x/+y) ==> +x+y
I just checked and that page has not been modifed (other than the ABNF change I made two weeks ago)
since May 14 2009. So this was a documented decision of the TC at that time.
I will start a separate thread on this specific topic so we can discuss it in advance of this week's call (and
of course we will discuss it on the call).
=Drummond
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