Identical-Priority XRD "URI" Elements...

["David Fuelling" <david.fuelling@cordance.net>]

Hey List,

I'm looking for some guidance...

I've been thinking about how to enable what I call "two-headed auth" in OpenID (which is where two OP's must provide a valid assertion to an RP before the RP grants access to protected resources), and have come up with one paticular way of doing this[1].

Basically, this just overrides (clarifies?) some of the behavior of XRI Resolution         2.0[2], section 4.3.3(3).  This section currently indicates that a consuming application which encounters multiple, identical-priority elements should just pick one of these elements at random.  My "extension/clarification" instead says that the consuming application SHOULD utilize both of the elements in tandem (instead of just one at random).  The net effect is this enables and instructs an RP to use 2 OP's to verify ownership of a particular OpenID. 

So, I have the following questions relating to this:

1. Is the behavior I've outlined in this message, and in my "very rough draft spec"[1], acceptable per the current version of XRI Resolution?  (The use of the word SHOULD leads me to beleive that it is).
   
   
2. However, if the answer is "no", how big of a deal would it be to loosen the language of section 4.3.3(3) to read something like this (my additions are indicated between brackets []):
   "If two or more instances of the same element type have identical priority attribute values (including the null value), the consuming application SHOULD [either] select one of the instances at random[, or utilize all of the equivalent priority elements together per the requirements of each particular Service]. This consuming application SHOULD NOT simply choose the first instance that appears in XML document order."

Thanks for any guidance here.  I'd also be open to hearing if there's a better way to do what I'm trying to do with XRD.

Thanks!

David


[1] http://wiki.openid.net/f/openid-provider-multiauth-extension-1_0-1.html
[2] http://docs.oasis-open.org/xri/2.0/specs/cd02/xri-resolution-V2.0-cd-02.html