Some people are on a patio and there is a fire.
The building is on fire.
If the building is on fire people aren't on the patio.
exists p1 p2 x1 x2.(exists x4.((x2 = x4) & n_fire(x4)) & exists x3.(on(x1,x3) & n_patio(x3)) & n_people(x1))
exists p1 x1.(n_building(x1) & exists x2.(on(x1,x2) & n_fire(x2)))