The dog is on the fence
A dog is on a fence.
dog is on the fence can also be said as dog is on a fence.
exists p1 x1 x2.(n_fence(x2) & n_dog(x1) & on(x1,x2))
exists p1 x1.(exists x2.(on(x1,x2) & n_fence(x2)) & n_dog(x1))