A kid is holding a rubber mallet.
The child is building things.
Just because the boy is holding a mallet does not mean that he is building things.  He could just be holding the mallet.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_hold(e1) & n_mallet(x2) & of(x2,x3) & n_rubber(x3) & n_kid(x1))
exists e1 x1 x2.(n_child(x1) & Theme(e1,x2) & Actor(e1,x1) & v_build(e1) & n_thing(x2))