A man is operating a piece of machinery.
A man sings in a choir.
The man cannot be operating a piece of machinery and singing in a choir at the same time.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_operate(e1) & of(x2,x3) & n_machinery(x3) & n_piece(x2) & n_man(x1))
exists e1 x1 x2.(in(e1,x2) & n_choir(x2) & Actor(e1,x1) & v_sing(e1) & n_man(x1))