While I think these promises are appropriate for a mature version of the
protocol, I do not think we should make them for 0.12.
We've just dreamed up version 0.1 of the protocol. It hasn't been used
in anger. Yes, we put some serious thought in it, and we even have
prototype code using it in libvirt, but let's face it, we're not
infallible: we *will* have to evolve stuff.
Without a real user, there is no real need to constrict evolution of the
protocol in such a harsh way. All it'll buy is is compatibility cruft.
Passage of time will bring us plenty of cruft without us setting
ourselves up for extras.
Let's cut ourselves some slack here, please.