A man with a backpack is observing an alligator.
The man is at a zoo
A man observing does not mean he is at the zoo.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_observe(e1) & n_alligator(x3) & with(x1,x2) & n_backpack(x2) & n_man(x1))
exists p1 x1.(n_man(x1) & exists x2.(at(x1,x2) & n_zoo(x2)))