A person rides a bike down a rocky hill.
A man is riding a bike down a hill.
Not every person riding a bike is a man.
exists e1 s1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & down(x2,x3) & n_hill(x3) & a_rocky(s1) & Theme(s1,x3) & n_bike(x2) & n_person(x1))
exists e1 x1 x2 x3.(down(e1,x3) & n_hill(x3) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bike(x2) & n_man(x1))