A bald man is skateboarding in the street.
A bald man is not skateboarding
He either is or isn't skateboarding.
exists e1 s1 x1 x2.(n_street(x2) & in(e1,x2) & Actor(e1,x1) & v_skateboard(e1) & n_man(x1) & a_bald(s1) & Theme(s1,x1))
exists s1 x1.(-exists e1.(Actor(e1,x1) & v_skateboard(e1)) & n_man(x1) & a_bald(s1) & Theme(s1,x1))