I hope this isn't too late. Perhaps not, the spec isn't listed as 1.0 yet. In any case, I feel really bad about not reviewing RSD before, expecially given that the RFC links to not one but three of my essays. I have three comments, which I will give in decreasing order of importance:
1) In the examples, there is an "rsd" namespace which is defined but never used. In order to use it, one would have to prefix each element with "rsd:". A simpler fix is to simply define this as the default namespace for the document, by dropping the ":rsd" entirely from the declaration. As it stands, I would say that the examples don't comply with the spec.
2) rpcLink presumes, well, RPC. With protocols like the RESTLog Interface, there is not a single URL, but rather a set of them. Yes, there is a base URL and one could munge it into this slot, but it really doesn't fit, and furthermore calling the slot RPC unnecessary provokes the more radical RESTians out there.
3) I would prefer to see a simple URL instead of a centrally managed list of "well known names". That's not to say that there can't be a list of known URLs. This is for two reasons: (1) to decentralize the maintenance, and (2) to provide more value by providing a direct link to the documentation of the protocol supported.