Several employees working on an underground rail track.
Several employees working on an above ground rail track.
One can not be underground and above ground simultaneously.
exists e1 s1 s2 x1 x2 x3.(on(e1,x2) & n_track(x2) & of(x2,x3) & n_rail(x3) & a_underground(s2) & Theme(s2,x2) & Actor(e1,x1) & v_work(e1) & n_employee(x1) & a_several(s1) & Theme(s1,x1))
exists e1 s1 s2 x1 x2 x3 x4.(on(e1,x2) & n_track(x2) & of(x2,x4) & n_rail(x4) & of(x2,x3) & n_ground(x3) & a_above(s2) & Theme(s2,x2) & Actor(e1,x1) & v_work(e1) & n_employee(x1) & a_several(s1) & Theme(s1,x1))