A young man is sitting in front of a drum.
The man sat on top of the drum.
On can either be in front of something or on top of it, but not both simultaneously.
exists e1 s1 x1 x2 x3.(in(e1,x2) & of(x2,x3) & n_drum(x3) & n_front(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1) & a_young(s1) & Theme(s1,x1))
exists e1 x1 x2 x3.(n_drum(x3) & n_man(x1) & on(e1,x2) & of(x2,x3) & n_top(x2) & Actor(e1,x1) & v_sit(e1))