A baseball player is fielding a ball.
A human chases a ball.
When a baseball player is fielding a ball a human chases it.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_field(e1) & n_ball(x3) & n_player(x1) & of(x1,x2) & n_baseball(x2))
all x1.(n_ball(x1) -> exists s1 x2.(a_topic(x2) & for(x2,x1) & n_chase(x2) & a_human(s1) & Theme(s1,x2)))