Re: [idn] One profile for domain names, or many?

["Adam M. Costello" <idn.amc+0@nicemice.net.RemoveThisWord>]

Here is my attempt at wording to clearly delimit the scope of IDNA and
Nameprep without precluding any future directions:

Applicability of Nameprep:

    When ToASCII or ToUnicode is applied to a label, the proper
    Stringprep profile for that label MUST be used.  Nameprep is the
    proper profile for all types of labels that do not specify a
    profile, which includes all types that predate IDNA (for example,
    host name labels and mail domain labels).  In the future the IETF
    might or might not define new types of labels that use other
    profiles with IDNA.

Applicability of IDNA:

    IDNA MAY be used with all types of textual domain names and textual
    domain labels that do not explicitly forbid the use of IDNA, which
    includes all types that predate IDNA (for example, host names and
    mail domain names).  In the future the IETF might or might not
    define new types of textual domain names/labels that forbid the use
    of IDNA.

    IDNA cannot be used with domain labels that contain non-textual
    data.  For example, in the current DNS protocol [RFC1034] [RFC1035]
    labels can contain octet values greater than 0x7F, but there is no
    defined interpretation of those values as characters.  Therefore
    IDNA cannot be used with DNS labels containing octet values greater
    than 0x7F.

With this policy, I think we could publish IDNA now and defer the
one-vs-many-profiles decision until later.  We can make a more informed
decision after the effort to formalize the label types has succeeded or
failed.

I think this policy would make it clear how to use IDNA today, and would
leave the IETF with three options when people ask to define a new label
that doesn't use Nameprep:

 1) Use a STD-13 binary.
 2) Use a text label that forbids the use of IDNA.
 3) Use a text label that requires fooprep with IDNA.

We could in the future decide that one or two of these options are
undesirable and should never be used, but for the moment we can leave
them all open.

What do people think of this?

AMC