Access-preserving limits

This is the access-preserving endpoint interface in CheungHawk04A,CheungHawk04B. A unitary swapping $R$ and $B$ changes the recovery task and is not an admissible local identification.

If the endpoint residual is fixed pure, endpoint radiation is an isometric encoding. A mixed fixed residual gives the syndrome normal form. An infinite endpoint syndrome need not admit a finite decoder program.