Sorting is not going to work for all locales simply by using allkeys.txt sadly.

To start understanding, try looking at http://oss.software.ibm.com/icu/userguide/Collate_Intro.html

http://oss.software.ibm.com/icu/userguide/Collate_API.html has some useful links as well.

You'll also have to look at the official Unicode consortium docs as well. http://www.unicode.org

Not really much fun I'm afraid :)