Someone riding sideways on a motorcycle.
A person is on a motorcycle.
A person refers to someone.
exists e1 x1 x2.(on(e1,x2) & n_motorcycle(x2) & Actor(e1,x1) & v_sideway(e1) & n_riding(x1))
exists p1 x1.(exists x2.(on(x1,x2) & n_motorcycle(x2)) & n_person(x1))