Currently, if a locale sensitive service provider wants to declare its available locales in getAvailableLocales() method, it has to list all possible combinations. For example, if the provider offers a unique object when some specific variant is specified, e.g., "calendar=japanese", it has to declare all the existing locale combinations with that variant, such as, en_US_calendar=japanese, en_GB_calendar=japanese, ...

This is not efficient and in fact, it would not work when new locales are added. Some mechanism to specify such an abstract locale set is needed.