A man with a dog.
The dog is on a leash.
Just because there is A man with a dog does not mean the dog is on a leash.
exists x1 x2.(a_topic(x1) & with(x1,x2) & n_dog(x2) & n_man(x1))
exists p1 x1.(n_dog(x1) & exists x2.(on(x1,x2) & n_leash(x2)))