Re: RTL PUA?

On 08/21/2011 08:19 AM, Asmus Freytag wrote:
> The best default would be an explicit "PU" - undefined behavior in the
> absence of a private agreement.

Hm -- but really this would only serve to allay concerns like Michael's
stemming from a presumption that the BC is "deeper" than other
characters (which I should concede is not entirely false). But you can't
define explicit undefined values for *all* properties (even those that
you can change despite stability) can you?

> There are some properties where stability guarantees prevent adding a
> new value. In that case, the documentation should point out that the
> intended effect was to have a PU value, but for historical / stability
> reasons, the tables contain a different entry.

What are these properties? The standard says that the canonical
decomposition will not be changed. Mark Davis said the GC can not be
changed[*]. What else?

[* There is no need to *officially* change the GC of the PUA characters,
but PUA-supporting implementations will certainly need to be able to
handle letters, marks and numbers etc as if they were encoded
characters, and Mark has expressed he is fine by that.]

> Suggesting a "structure" on the private use area, by suggesting
> different default properties, ipso facto makes the PUA less private.
> That should be a non-starter.

I entirely agree (obviously).

-- 
Shriramana Sharma