A dog chews on a stick.
A dog is chewing.
dog chews is same as dog is chewing
exists e1 x1 x2.(on(e1,x2) & n_stick(x2) & Actor(e1,x1) & v_chew(e1) & n_dog(x1))
exists e1 x1.(Actor(e1,x1) & v_chew(e1) & n_dog(x1))