A man sits at a table.
A man is standing on a table.
If he sits, he is not standing.
exists e1 x1 x2.(at(e1,x2) & n_table(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1))
exists e1 x1 x2.(on(e1,x2) & n_table(x2) & Actor(e1,x1) & v_stand(e1) & n_man(x1))