People are having some kind of a day fair.
People are sell food at the fair.
Just because people are having some kind of day fair doesn't mean they are selling food.
exists e1 x1 x2 x3 x4.(Theme(e1,x2) & Actor(e1,x1) & v_have(e1) & of(x2,x3) & n_fair(x3) & of(x3,x4) & n_day(x4) & n_kind(x2) & n_people(x1))
exists p1 x1 x2.(n_fair(x2) & at(p1,x2) & exists s1 x3.((x1 = x3) & n_food(x3) & a_sell(s1) & Theme(s1,x3)) & n_people(x1))