The problem I have is that draft-ietf-impp-cpim-msgfmt lays out a
detailed set of requirements and explains how to use MIME. If S/MIME
is the right answer, much of the rationale can be omitted, except
perhaps a short statement that the environmental model is very much
like the one that email has. This is the message format RFC; it should
really point to the authoritative source for the desired encoding and
encapsulation. The rationale, if needed at all, should have been in
draft-ietf-impp-im, which is setting out the framework.
Beyond that, it isn't clear to me that they've said enough about how to
use CMS and S/MIME. There are lots of possible options and variations;
I don't know that all are useful or correct here. That's where I want
to defer to Russ.
I'd like -msgfmt- to keep its mouth shut about whether to use S/MIME; it's
not really its business, since that ties into the whole trust model issue.