% heating_k1 is true if kettle k1 is heating 
heating_k1 <-
   plugged_into_k1_p1 & 
   live_p1 & 
   turned_on_k1 & 
   filled_with_water_k1.

% plugged_into_k1_p1 is true if k1 is plugged into power outlet p1
plugged_into_k1_p1.
plugged_into_k2_p2.

% turned_on_k1 is true if k1 is turned on 
turned_on_k1.
turned_on_k3.

% filled_with_water_k1 is true if k1 is filled with water 
filled_with_water_k1.