A man sits and performs at a piano
A man is sleeping.
One cannot perform at a piano while sleeping
exists e2 e1 x1 x2 x3.(at(e2,x3) & n_piano(x3) & Actor(e2,x2) & v_perform(e2) & n_man(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1))
exists e1 x1.(Actor(e1,x1) & v_sleep(e1) & n_man(x1))