A woman sings while people dance.
A woman is performing.
If someone sings they are also performing
exists e1 x1 x2 x3.(while(e1,x2) & Time(x2,x3) & n_dance(x3) & n_people(x2) & Actor(e1,x1) & v_sing(e1) & n_woman(x1))
exists e1 x1.(Actor(e1,x1) & v_perform(e1) & n_woman(x1))