The boys are playing soccer.
Boys are playing soccer on a muddy field.
The boys are playing soccer but not necessarily on a muddy field.
exists e1 x1 x2.(n_boy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_soccer(x2))
exists e1 s1 x1 x2 x3.(on(e1,x3) & n_field(x3) & a_muddy(s1) & Theme(s1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_soccer(x2) & n_boy(x1))