A man rides a bicycle on a rocky trail along a large river.
Nobody is riding.
It can either be a man riding a bicycle, or nobody. Not both.
exists e1 s1 s2 x1 x2 x3 x4.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & along(x2,x4) & n_river(x4) & a_large(s2) & Theme(s2,x4) & on(x2,x3) & n_trail(x3) & a_rocky(s1) & Theme(s1,x3) & n_bicycle(x2) & n_man(x1))
-exists e1 x1.(Actor(e1,x1) & v_ride(e1) & n_person(x1))