The person is walking in the mountains.
A person is riding a staionary bike.
The person is walking and not riding a stationary bike.
exists e1 x1 x2.(n_mountain(x2) & n_person(x1) & in(e1,x2) & Actor(e1,x1) & v_walk(e1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bike(x2) & a_staionary(s1) & Theme(s1,x2) & n_person(x1))