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Subject: Status of XRD/XRDS effort at OASIS XRI TC

Here's a short status report on the XRD/XRDS metadata discovery effort at

Since XRIs as abstract identifiers have always needed a metadata discovery
format/protocol, the XRI 1.0 specs published in 2004 defined an XML format
called XRID (XRI Descriptors) together with a simple http(s) discovery
protocol. Early market feedback led to a second generation of XRI syntax and
XRID in 2005. 

At that point OpenID 2.0 was being born and it needed a discovery format
very similar to XRID. Discussions between the XRI TC and OpenID community
resulted in renaming XRID to XRDS, which was the XML wrapper element for a
sequence of one or more XRDs (Extensible Resource Descriptor). XRDS was
adopted as the metadata format for the Yadis discovery protocol for http(s)
URIs [1] used by OpenID Authentication 2.0. The Yadis protocol was
subsequently incorporated as Section 6 of XRI Resolution 2.0 [2], though in
practice OpenID implementations used only a subset of the features of XRDS.

At that juncture Eran, working on OAuth Discovery [3], wanted to formally
specify that core subset and more rigorously define the discovery protocol.
He started the XRDS-Simple mailing list to develop the XRDS-Simple spec [4].

In the meantime, the failure of the OASIS Standard vote on XRI 2.0 due to
opposition from the W3C TAG led to extensive dialog between the XRI TC and
the W3C TAG about both abstract identifiers and metadata discovery. Members
of the TAG and the www-tag mailing list pointed out several architectural
issues with the Yadis discovery protocol. They also shared their experience
with the general issue of metadata discovery [5], pointed out the relevance
of the W3C POWDER effort to this topic area [6], and said they were working
on a TAG finding on "Uniform Access to Metadata" [7].

The XRI TC concluded that we would need a third generation of metadata
discovery that:

a) is as simple as possible.
b) works uniformly for both URIs and XRIs.
c) is compatible with AWWW design principles and W3C TAG feedback.
d) can be used interoperably by XRI, OpenID, OAuth, OpenSocial, SAML, IMI,
and other Internet identity/security/data sharing infrastructure.

Eran joined the XRI TC to lead that work as editor of a new specification
called XRD. He led an all-afternoon session on XRD at Internet Identity
Workshop last Tuesday as well as an all-day session on XRD as part of the
XRI TC face-to-face last Thursday. Key conclusions from that meeting [8]

* XRD will be a separate spec from XRI 3.0.
* XRD will be the successor to both XRDS and XRDS-Simple (most of the XRDS
elements that were unique to XRI Resolution 2.0 will be deprecated).
* XRI 3.0 resolution can and should be simplified to the point where it is
just a profile of XRD. 
* XRD discovery should have trusted mode(s) which will most likely will meet
the requirements for XRI 3.0 trusted resolution. (The XRD Simple Sign
proposal [9] is being developed for this purpose.)

The TC also decided to start holding two separate weekly telecons -- one on
XRD and one on XRI 3.0 -- to advance both specs as quickly as possible and
let TC members who only want to focus on one or the other do that. The
current plan is for one call to be from 1-2PM Pacific Time and the second
from 2-3PM PT. (The XDI TC telecon that normally runs from 1-2PM PT would be
moved back to 12-1PM PT).

Like all OASIS TCs, the XRI TC is open to anyone to join [10] as long as
they agree to OASIS IPR rules [11]. If you interested in being part of the
XRD work directly (and have not already contacted me via the XRDS-Simple
list), feel free to drop me a note for more details.


[1] http://yadis.org/papers/yadis-v1.0.pdf
[2] http://docs.oasis-open.org/xri/2.0/specs/xri-resolution-V2.0.html 
[3] http://oauth.net/discovery/1.0 
[4] http://xrds-simple.net/core/1.0 
[5] http://esw.w3.org/topic/FindingResourceDescriptions
[6] http://www.w3.org/2007/powder/
[7] http://www.w3.org/2001/tag/doc/uniform-access.html 
[8] http://wiki.oasis-open.org/xri/FaceToFaceAgenda
[9] http://wiki.oasis-open.org/xri/XriThree/SimpleSign 
[10] http://www.oasis-open.org/join/ 
[11] http://www.oasis-open.org/who/policies_procedures.php

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