Corrigendum #9

Asmus Freytag asmusf at
Mon Jun 2 11:35:54 CDT 2014

On 6/2/2014 9:08 AM, Mark Davis ☕️ wrote:
> The problem is where to draw the line. In today's world, what's an 
> app? You may have a cooperating system of "apps", where it is 
> perfectly reasonable to interchange sentinel values (for example).

The way to draw the line is to insist on there being an agreement 
between sender and ultimate receiver, and an pass-through agreement (if 
you will) for any intermediate stage, so that the coast is clear.

What defines an "implementation" in this scenario, is the existence of 
the agreement.

What got us into trouble is that the negative case (pass-through) was 
not well-defined, and lead to people assuming that they had to filter 
any incoming noncharacters.

Because noncharacters can have any interpretation (not limited to 
interpretations as characters), it is much riskier to send then out 
oblivious whether the intended recipient is part of the same agreement 
on their interpretation as the sender. In that sense, they are not mere 
PUA code points.

The other aspect of their original design was to allow code points that  
recipients were free no to honor or preserve, if they were not part of 
the agreement (and hadn't made an explicit or implicit pass-through 
agreement). Otherwise, if anyone expects them to be preserved, no 
application like Word, would be free to use these for purely internal use.

Word thus would not be a tool to handle CLDR data; which may be 
disappointing to some, but should be fine.

> I agree with Markus; I think the FAQ is pretty clear. (And if not, 
> that's where we should make it clearer.)
> Mark <>
> /
> /
> /— Il meglio è l’inimico del bene —/
> //
> On Mon, Jun 2, 2014 at 6:02 PM, Shawn Steele 
> <Shawn.Steele at <mailto:Shawn.Steele at>> wrote:
>     I also think that the verbiage swung too far the other way.  Sure,
>     I might need to save or transmit a file to talk to myself later,
>     but apps should be strongly discouraged for using these for
>     interchange with other apps.
>     Interchange bugs are why nearly any news web site ends up with at
>     least a few articles with mangled apostrophes or whatever (because
>     of encoding differences).  Should authors’ tools or feeds or
>     databases or whatever start emitting non-characters from internal
>     use, then we’re going to have ugly leak into text “everywhere”.
>     So I’d prefer to see text that better permitted interchange with
>     other components of an application’s internal system or partner
>     system, yet discouraged use for interchange with “foreign” apps.
>     -Shawn
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