[OpenID] XRD: <hm:Host> inside <Subject>?

[Manger, James H]

How about putting <hm:Host> inside <Subject>?



When there is a single URI identifying the resource described by the XRD use:

  <Subject><URI> http://example.com/thingA</URI></Subject>



When the XRD describes a host use:

  <Subject><hm:Host>example.com</hm:Host>

                      <hm:Host>www.example.com</hm:Host></Subject>



When the XRD does not specify an identity for the resource(s) it describes use:

  <Subject/>





1.       <Subject> can be mandatory (which some want).

2.       A <URI> child element is already used in <Link> elements so it “fits” with the specs style.

3.       An empty <Subject> element unambiguously says “no identify here for the resource this metadata describes — use something else”.

4.       Other specs (eg host-meta) can define their own elements to identify the subject, using their own XML namespaces instead of a new registry.

5.       An application can tell when it doesn’t understand how the subject is being identified — there will be unrecognized elements in <Subject>.



Point 5 prevents an application (that understands XRD but not, say, host-meta) misinterpreting an XRD that has an unrecognized element providing a role similar to the absent <Subject>.



James Manger

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