Several people work on a machine.
A machine is being worked on by several people
work on a machine can be written as machine is being worked on.
exists e1 s1 x1 x2.(on(e1,x2) & n_machine(x2) & Actor(e1,x1) & v_work(e1) & n_people(x1) & a_several(s1) & Theme(s1,x1))
exists e1 s1 s2 x1 x2.(Actor(e1,x2) & n_people(x2) & a_several(s2) & Theme(s2,x2) & a_on(s1) & Manner(e1,s1) & Theme(e1,x1) & v_work(e1) & n_machine(x1))