Four people stand in the middle of a library gathering children's books.
The four people are sitting.
The four people sitting could not have been the one that stand at the same time.
exists e1 x1 x2 x3 x4 x5 x6.(n_middle(x2) & in(e1,x2) & of(x2,x6) & n_book(x6) & of(x6,x3) & n_child(x3) & of(x3,x5) & n_gathering(x5) & of(x3,x4) & n_library(x4) & Actor(e1,x1) & v_stand(e1) & n_people(x1) & card_eq_4(x1))
exists e1 x1.(n_people(x1) & card_eq_4(x1) & Actor(e1,x1) & v_sit(e1))