The original STRIPS planner was designed to control Shakey the robot. The figure above shows a version of Shakeys world consisting of four rooms lined up along a corridor, where each room has a door and a light switch. One room has an evil baby. If the light gets flipped 'on' in a room that the evil baby is in, then the baby will switch it 'off' (so, no action occurs). The actions in Shakey's world include moving from place to place, playing music to lure the evil baby to another room, and turning light switches on and off. Shakeys four actions are the following:

1. Go(x, y, r), which requires that Shakey be At x and that x and y are locations In the same room r. By convention a door between two rooms is in both of them.

2. Lure the evil baby from b from location x to location y in a new room 'r': Lure(b, x, y, r). You will need the predicate Baby. The baby cannot be left in the corridor.

3. Turn a light switch on or off: TurnOn(s,b); TurnOff (s,b). To turn a light on or off, Shakey must not be in the same room as the evil baby and at the light switchs location.

Write PDDL sentences for Shakeys four actions and the initial state from the figure. Construct a plan for Shakey to change the lights in rooms 4, 2, and 1 (switch on if it is off; switch off if it is on).

Switch 4 Door 4 Room 4 Switch 3 Door 3 Room 3 Shakey Corridor Switch 2 Door 2 Room 2 Switch 1 Door1 Room 1 Switch 4 Door 4 Room 4 Switch 3 Door 3 Room 3 Shakey Corridor Switch 2 Door 2 Room 2 Switch 1 Door1 Room 1