I did not intend it to suggest that dimensions must be scalar, quite the contrary. I plan to add some examples which make this more clear. It is supposed to reflect increasing complexity, both from a human viewpoint and from the viewpoint of an extensible negotiation mechanism. If there were not multiple values to choose from, there would be no negotiation. Here is a rewrite of the first part of the form, please say if you like this better.
Some fields are optional.