A particular power plant had many valves situated around the plant. When something had to be changed, operators had to physically walk to the room where a particular valve was located, and move it by hand to the desired setting. The physical valve was controlled by a lever that looked something like this. If the lever was in between the two positions, the valve would be partially open.
The valves recently became motorized and controlled by computer. Janet E. Hacker was hired to create a new interface widget that represented these valves on the operator's display. After thinking about it, she decided that this valve could be powerfully modeled by combining conventional buttons, popup menus and dialog boxes as follows:
Here's how the widget worked.
- left mouse button: pop up the menu (shown on the right)
- middle mouse button: turn the valve off
- right mouse button: turn the valve all the way on
- shift left mouse button: set the valve slightly open
- shift middle mouse button: set the valve mostly open
- shift right mouse button: bring up value numeric setting dialog box
Using your knowledge of design concepts of everyday things (summarized as the concepts below), critique this design, sketch an alternative control, and justify the new control using these design concepts.
-Affordances -Transfer effects -Causality -Idioms & Population stereotypes -Visible constraints -Conceptual model -Mapping -Individual differences