UTC position on IDNA mapping

L2/077

From: Mark Davis
To: UTC
Date: 2009-2-4
Re: UTC position on IDNA mapping

The following is my draft to capture the results of the discussions in the UTC meeting on 2009-2-4 (with some renumbering):

Given a choice among the different options for mapping in IDNA2008, the UTC has the following preferences. Note that UTS #46 contains a mapping that is based on the same principles as IDNA2003, but has exceptions for the special cases required by IDNA2008 (sharp s, etc.).

1. Any Local Mapping allowed (current situation in IDNA2008) - Very bad.
We foresee that in practice UTS 46 mappings would be used to maintain compatibility with IDNA2003. However, it could also encourage incompatible localized mappings, which would cause interoperability and security problems.

2. No mapping allowed - Very bad. And unenforceable

3. Silent on mapping - Bad
We foresee that in practice UTS 46 mappings would be used to maintain compatibility with IDNA2003. The danger here is the same as for #1; it is not quite as bad as mentioning local mapping explicitly, thereby implicitly encouraging it.

4. Discourage local mapping except for "compatibility with IDNA2003" - Better
We foresee that in practice UTS 46 mappings would be used to maintain compatibility with IDNA2003. Operationally this is the same as #3, except that it is more explicit about the recommendation.

5. Case Mapping incorporated into protocol - Better
The UTC would modify UTS 46 so as to remove case mappings. We foresee that in practice the modified UTS 46 mappings would be used to maintain compatibility with IDNA2003.

6. Case + Width Mapping incorporated into protocol - Better
The UTC would modify UTS 46 so as to remove case mappings and width mappings. We foresee that in practice the modified UTS 46 mappings would be used to maintain compatibility with IDNA2003.

7. UTS#46 Mappings incorporated in protocol - Best
The UTC would discontinue UTS 46, as there would be no need for it.