A birthday party is going on with lots of people celebrating.
People are celebrating a birthday.
If people at a birthday party are celebrating, they're celebrating a birthday.
exists e2 e1 s1 x1 x2 x3 x4 x5.(with(e1,x3) & of(x3,x4) & Actor(e2,x5) & v_celebrate(e2) & (x4 = x5) & n_people(x4) & n_lot(x3) & a_on(s1) & Manner(e1,s1) & Actor(e1,x1) & v_go(e1) & n_party(x1) & of(x1,x2) & n_birthday(x2))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_celebrate(e1) & n_birthday(x2) & n_people(x1))