A yellow tractor sits on a hillside.
A yellow tractor is plowing the field.
A tractor on a hillside is not necessarily plowing the field.
exists e1 s1 x1 x2.(on(e1,x2) & n_hillside(x2) & Actor(e1,x1) & v_sit(e1) & n_tractor(x1) & a_yellow(s1) & Theme(s1,x1))
exists e1 s1 x1 x2.(n_field(x2) & Theme(e1,x2) & Actor(e1,x1) & v_plow(e1) & n_tractor(x1) & a_yellow(s1) & Theme(s1,x1))