When and why

[Paul Hoffman]

At 10:16 AM -0400 4/14/09, Vint Cerf wrote:
>The dialogue among Paul Hoffman, Andrew Sullivan, Pete Resnick and Patrik Faltstrom suggests to me that a definition of Mapping (prior to lookup) should be undertaken by the WG but that its use might  be determined by application context.

That seems to be the rough consensus, yes (even though I'm again in the minority here...).

> If that compromise is adopted, the Mapping would be recommended in cases where IDNA2003 compatibility is desired/needed but that mapping on lookup is not absolutely required under all circumstances.

That is not the description for "why" we have been discussing. I think a better descriptions is that that the mapping would be recommended in cases where user input might be predicted to need mapping, such as where the input might have mixed case, combining characters, and compatibility characters. IDNA2003 inherently handled all of those, but that fact is not the main motivator for wanting to standardize the optional use in IDNA2008.