Small comments on WD-04:
Sec 2.2.3, I think the schema snippet is missing the match attribute?
With regard to keys in links, it may be reasonable to say something very brief about the lack of any built-in requirements for matching them. Perhaps in section 2.4.1, just something like:
"KeyInfo is included from the [XML Signature] schema, and provides the digital signature metadata necessary to validate interaction with the linked resource. The specifics of this validation process are left to other specifications to define."
Sec 3.1.1, s/addtional/additional
Sec 4, I have a few suggestions to correct some issues inherited from the SAML text, which recently have caused some confusion.
In 4.1, I suggest not calling out RSA there. That's a matter for conformance, and I would something to section 5 that lists the MTI algorithm(s) to support. I would replace with:
"Any algorithm defined for use with the XML Signature specification MAY be used."
In 4.3, suggest rephrasing to:
"Use of Exclusive Canonicalization facilitates the verification of signatures created over XRD instances when placed into a different XML context than present during signing.
Note that use of this algorithm alone does not guarantee that a particular signed object can be moved from one context to another safely, nor is that a requirement of signed XRD instances in general, though it MAY be required by particular profiles."
-- Scott
