An umpire marking a base.
A umpire  on the field
One has to be on the field to be marking a base.
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_mark(e1) & n_base(x3) & (x1 = x2) & n_umpire(x1))
exists x1 x2.(n_field(x2) & a_topic(x1) & on(x1,x2) & n_umpire(x1))