A zebra is nibbling on some grass.
The zebra has teeth.
A zebra can nibble on grass without having teeth.
exists e1 x1 x2.(on(e1,x2) & n_grass(x2) & Actor(e1,x1) & v_nibble(e1) & n_zebra(x1))
exists e1 x1 x2.(n_zebra(x1) & Theme(e1,x2) & Actor(e1,x1) & v_have(e1) & n_tooth(x2))