menu, along with command (and bb too...), is another element like button and input that has a "type" attribute that takes an enumerated list of possible values -- and one whose semantics differ depending on what the @type value is; e.g, for menu, it's either not really even a menu, but instead a "toolbar", or it has the more specific semantics of being a "context menu" or (when no type attribute is specified at all) it has the more-general semantics of being just "list of commands". It could in fact be modeled as three separate elements named commands, toolbar, contextmenu (or whatever), so it makes some sense to model it that way in the schema (that is, similar to the way the input and button elements are already modeled).

Anyway, the attached patch attempts to do that (along with removed the "autosubmit" attribute from menu).