RE: [xri] attributes on <Extensions>

Will Norris wrote on 2009-09-01:
> I don't think we actually talked about it... do we want to allow
> arbitrary attributes on the <Extensions> element like we do everything
> else?  Currently, the schema does not allow for this.  Personally, I
> don't see any harm in it.  But to be fair, nor do I really see much
> value in it for extension authors.

No, the model should be clean such that any extension appears in an element
inside that block. There's nothing to use to interpret an attribute
appearing in that element.

-- Scott