A man sits at a table.
A man is sitting at a table.
A man either sits or the man is sitting at a table.
exists e1 x1 x2.(at(e1,x2) & n_table(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1))
exists e1 x1 x2.(at(e1,x2) & n_table(x2) & Actor(e1,x1) & v_sit(e1) & n_man(x1))