A black dog running.
A llama is being sheared.
there can be either a dog or a llama.
exists e1 s1 x1 x2.(a_topic(x1) & Actor(e1,x2) & v_run(e1) & (x1 = x2) & n_dog(x1) & a_black(s1) & Theme(s1,x1))
exists e1 x1.(Theme(e1,x1) & v_shear(e1) & n_llama(x1))