Yadis/XRDS Service Element URI Question

[David Fuelling]

Hey All,

I'm working on a draft OpenId 2.0 extension [1] and am looking for guidance
on how to define a Yadis Service Element that includes a URI Template
(instead of a real URI).

At first, I thought that the following would be ok:

<Service xmlns="xri://$xrd*($v*2.0)">
  <Type>http://openid.net/srv/oeat/1.0/ett</Type>
  <URI>https://{username}.example.com/</URI>
</Service>

However, 'https://{username}.example.com/' is not a valid URI, since the '{'
and '}' characters are reserved per the URI specification.

So, should I simply "percent encode" the URI above to be
'https://%7Busername%7D.example.com/', or should I define a new Service
Element child, like the following:

<Service xmlns="xri://$xrd*($v*2.0)">
  <Type>http://openid.net/srv/oeat/1.0/ett</Type>
  <TemplateURI>https://{username}.example.com/</TemplateURI >
</Service>

Does Yadis/XRDS require the presence of a URI child in a service element?
Is it legal to define new children elements?  Is that advisable?

Thanks!

David

[1]
http://www.sappenin.com/openid/ext/oet/openid-email-transform-extension-1_0.
html