Tagging transliterations from a specific script

[Michael Everson]

On 17 Mar 2011, at 14:07, Doug Ewell wrote:

> The use case of identifying the script in which content IS written is MUCH, MUCH more common than the use case of identifying the script in which it was ORIGINALLY written before being transliterated to some other script.  This latter scenario is very much a special case, and on no account does it justify overhauling BCP 47 to make the order of subtags flexible and their meaning dependent on their relative order.

Then why not revise it to add some sort of generic transliteration subtag that could handle source/target transliterations dynamically? Isn't such extensibility part of the rationale of this scheme? 

Michael Everson * http://www.evertype.com/