A large black and brown dog is carrying something in its mouth while walking on grass.
The dog is carrying a bone in it's mouth.
A dog carrying something in its mouth is not necessarily a bone.
exists e2 e1 s1 s2 s3 x1 x2 x3 x4.(while(e1,e2) & on(e2,x4) & n_grass(x4) & Actor(e2,x1) & v_walk(e2) & Theme(e1,x2) & Actor(e1,x1) & v_carry(e1) & in(x2,x3) & n_mouth(x3) & of(x3,x1) & n_thing(x1) & n_thing(x2) & n_dog(x1) & a_brown(s3) & Theme(s3,x1) & a_black(s2) & Theme(s2,x1) & a_large(s1) & Theme(s1,x1))
exists e1 p1 x1 x2 x3.(n_thing(x1) & n_dog(x1) & Theme(e1,x2) & Actor(e1,x1) & v_carry(e1) & exists x4.((x3 = x4) & n_mouth(x4)) & (x2 = x3) & in(x2,x1) & n_bone(x2))