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Subject: Minutes: XRI TC Telecon 8-9AM PT Tuesday 2009-01-27

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

Date:  Tuesday, 27 January 2009 USA
Time:  8:00AM - 9:00AM Pacific Time (16:00-17:00 UTC)


Markus Sabadello
Peter Davis
George Fletcher
Drummond Reed 
Eran Hammer-Lahav 
John Bradley
Brian Eaton 


Note that the agenda for Tuesday calls is now on the Self-Service Agenda


The agenda items below are listed on that page with dated/numbered headings.


The first issue is about the relationship of an XRD and the resource it
describes. We discussed the terminology around this and agreed that to our
understanding of the Architecture of the World Wide Web, every URI
identifies a unique resource, and it is only via other means that one can
establish if multiple URIs identify the same resource, in which case that
one resource must be an "abstract" or "aggregate" resource (sometimes called
an entity).

Brian: what's the difference between <About> and <URI>?

The key question we discussed was: is the relationship of an XRD to resource
1-to-1 or 1-to-many? In other words, can a single XRD describe multiple

The assumption up through XRI 2.0 is that the relationship is 1-to-1. Under
this assumption, an XRD can only have a CanonicalID and any other
identifiers included to describe that resource must all be synonyms
(identifier for the same resource).

However Eran's question introduces a new way of looking at it. A single XRD
may describe an entire set of resources. His proposed <About> element is a
way for the XRD to identify such resource(s), but it is optional and one-way
pointer from the XRD to any resource it describes.

Peter suggested that this could be considered an "anonymous XRD" or
"wildcard XRD". This would mean it is a set of metadata that describes any
one of a group of resources, such as all the web pages at a site. Such an
XRD would not have a CanonicalID because it does not represent a single
resource, but a set of resources.

Peter gave the example Walmart having a single XRD that describes all RFID
tags in its namespace. 

He noted this wildcard XRD may introduce some trust processing challenges.
The consuming application still needs to know that resource X is
authoritatively described by the XRD Y. In the past, XRDs have used
CanonicalID to do this, but that does not have to be the only mechanism.

Peter suggested that instead of a fixed CanonicalID or URI element, the XRD
may support a URI template just as has been proposed for /site-meta. This
"wildcard CanonicalID" would match any URI which the XRD was authorized to
describe. That could have the benefit of allowing an application to cache a
fixed XRD "template" and continue to use it to describe any URI meeting that
template, which could have significant performance advantages. George
suggested that there should be a way to explicitly declare that the scope of
the XRD is beyond a single resource.

There seemed to be general support for this wider definition of the
applicability of an XRD due to the obvious practical benefits. However we
ran out of time to discuss it further on this call. We agreed to continue
the discussion on the list and on Thursday's telecon.


Regular Thursday telecon 2-3PM PT (22:00-23:00 UTC). Drummond noted he would
not be able to attend due to travel; Peter will facilitate the agenda and
the call.

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