A user interface having a plurality of user interface elements including: background,
passive elements such as frames and borders, information display elements that
present information from application software operating on the control unit, and
control elements that cause application software operating on the control unit
to initiate programmed behaviors. The user interface as a whole is contextually
sensitive in that the appearance of user interface elements (e.g., color, size,
font, contrast, order, grouping, arrangement, etc.) and/or the behavior of user
interface elements are varied in a manner that is dependent on the context of the
control unit. The context of the control unit is represented by state information
known to the control unit, which includes context-specific state information known
to a particular control unit as well as global context information known to multiple
or all control units in a system.