A tan dog runs on a sandy beach.
The dog is outside.
Only one dog is mentioned, so 'the' is appropriate; since it runs on a beach and all beaches are outside, the dog must be outside.
exists e1 s1 s2 x1 x2.(on(e1,x2) & n_beach(x2) & a_sandy(s2) & Theme(s2,x2) & Actor(e1,x1) & v_run(e1) & n_dog(x1) & a_tan(s1) & Theme(s1,x1))
exists s1 x1.(n_dog(x1) & Theme(s1,x1) & a_outside(s1))