There was some agreement on this from the room. The purpose of this message is to see if there is agreement on the mailing list too. I think people want to proceed with. The result is below. Note that there are some loose ends with respect to syntax and terminology definitions.
Comments are welcome.
This can be done by including an Alternates header, which lists the available variants, in the response. The Alternates header can also be used in a response which does not include a version itself, but simply informs the client that multiple versions are available. The Alternates header describes all available variants the server has available. The description for each variant includes an URI from which this variant can be retrieved. The Alternates header can also contain directives for any subsequent negotiation process.