On garden lawn, black dog is retriving an object.
A black lab is fetching a stick.
Just because it is  On garden lawn, black dog is retriving an object does not mean the dog is a lab or that the object is a stick.
exists e1 s1 x1 x2 x3 x4.(on(e1,x3) & n_lawn(x3) & of(x3,x4) & n_garden(x4) & Theme(e1,x2) & Actor(e1,x1) & v_retrive(e1) & n_object(x2) & n_dog(x1) & a_black(s1) & Theme(s1,x1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_fetch(e1) & n_stick(x2) & n_lab(x1) & a_black(s1) & Theme(s1,x1))