It looks like the talk is limited to instructions on how to produce well formed utf-8 string transformations. Once you go farther than that your into the nitty

It looks like the talk is limited to instructions on how to produce well formed utf-8 string transformations. Once you go farther than that your into the nitty gritty of internationalization which is itself a moving target as cultures change. For example how should strrev handle BIDI control characters? When is the unicode BIDI algorithm appropriate and when is it not? (hint: formulas look pretty messed up with it). At some point these become application specific.