A man in a chef's hat is preparing food.
A man is cooking hamburgers.
Preparing food doesn't imply that the food is hamburgers.
exists e1 x1 x2 x3 x4.(Theme(e1,x4) & Actor(e1,x1) & v_prepare(e1) & n_food(x4) & in(x1,x3) & n_hat(x3) & of(x3,x2) & n_chef(x2) & n_man(x1))
exists p1 x1.(exists s1 x2.((x1 = x2) & n_hamburger(x2) & a_cooking(s1) & Theme(s1,x2)) & n_man(x1))