A group of people are gathered at some type of outdoor event.
The outdoor field was empty.
If the people were gathered at an outdoor event then it would not be empty.
exists e1 s1 x1 x2 x3 x4.(at(e1,x3) & of(x3,x4) & n_event(x4) & a_outdoor(s1) & Theme(s1,x4) & n_type(x3) & Theme(e1,x1) & v_gather(e1) & of(x1,x2) & n_people(x2) & n_group(x1))
exists s1 s2 x1.(n_field(x1) & a_outdoor(s1) & Theme(s1,x1) & Theme(s2,x1) & a_empty(s2))