A child looks at a robot.
The child looks at a pig.
a child cannot look at a robot and a pig at the same time
exists e1 x1 x2.(at(e1,x2) & n_robot(x2) & Actor(e1,x1) & v_look(e1) & n_child(x1))
exists e1 x1 x2.(n_child(x1) & at(e1,x2) & n_pig(x2) & Actor(e1,x1) & v_look(e1))