A worker in a blue hat is fixing the wall.
A worker is hammering.
There are multiple ways to fix a wall (watching, spackling, etc.) so you cannot infer the worker is hammering.
exists e1 s1 x1 x2 x3.(n_wall(x3) & Theme(e1,x3) & Actor(e1,x1) & v_fix(e1) & in(x1,x2) & n_hat(x2) & a_blue(s1) & Theme(s1,x2) & n_worker(x1))
exists e1 x1.(Actor(e1,x1) & v_hammer(e1) & n_worker(x1))