Computers as Components, 2nd Edition

8.7 Design Example: Elevator Controller 431

Sensor*

hit : boolean

Coarse-sensor* Fine-sensor*

Motor*

speed : {off, slow, fast}

Master-control-panel*

Floor-control-panel*

up, down : boolean

Car-control-panel*

floors[1..F] : boolean

emergency-stop : boolean

open-door, close-door :

boolean

master-stop( )

elevator-positions[1..H][1..F] : boolean

master-stop-indicator : boolean

FIGURE 8.28

Physical interface classes for the elevator system.

objects.The only difference among the sensors to the elevator controller is whether

they indicate coarse or fine positions;other physical distinctions among the sensors

do not matter.

The Car and Floor classes, which describe the