A worker is cleaning the floor of a big outdoor fountain.
The worker is not cleaning the dirty fountain.
not cleaning contradicts cleaning
exists e1 s1 s2 x1 x2 x3.(n_floor(x2) & Theme(e1,x2) & Actor(e1,x1) & v_clean(e1) & of(x2,x3) & n_fountain(x3) & a_outdoor(s2) & Theme(s2,x3) & a_big(s1) & Theme(s1,x3) & n_worker(x1))
exists x1 x2 x3.(n_fountain(x2) & of(x2,x3) & n_dirty(x3) & n_worker(x1) & -exists e1.(Theme(e1,x2) & Actor(e1,x1) & v_clean(e1)))