2. in : |R|
IdLnk
3. out : |R|
IdLnk
4.
i:|R|.
4. R(source(in(i))) & R(destination(out(i)))
4. & source(out(i)) = i
4. & & destination(in(i)) = i
4. & & in(destination(out(i))) = out(i)
4. & & out(source(in(i))) = in(i)
5.
i,j:|R|. 
k:
. 
x.destination(out(x))^k(i) = j
6. i : |R|
7. k :
8.
x.destination(out(x))^k(i) = i
9. (
x.destination(out(x))) 
|R||R|
10. i@0 : |R|
11.
i@0 = i
12.
j:|R|. n:k. x.destination(out(x))^n(i) = j
13. n :
k
14.
x.destination(out(x))^n(i) = i@0
i@0 = x.destination(out(x))^n(i) |R|
