A man is biking on a hill.
the man is walking
Biking and walking are separate actions.
exists e1 x1 x2.(on(e1,x2) & n_hill(x2) & Actor(e1,x1) & v_bike(e1) & n_man(x1))
exists e1 x1.(n_man(x1) & Actor(e1,x1) & v_walk(e1))