Language Data Consistency

We have a set of tests for consistency in the data for language, script, and country. The following is a draft description what those consistency checks should aim for.

Default script, language

• 1. For each script encoded in Unicode, the default* language is present in the script metadata.
     1. For each language used in CLDR, there is a default* script

* default = most used in writing; currently if modern, otherwise historical.

Implications for Language-Country population data (LCPD)

1. If a base-language has a CLDR locale, then it is in the LCPD for at least one country.
2. If there is a CLDR country locale for a language, then that language+country is in the LCPD.
   1. For each country, get the language most widely used as a written language in that country. That language+country combination is in the LCPD.
   2. When a significant proportion of the language use in a country is in a non-default script, that script is marked in the LCPD.
   3. When a script is not EXCLUDED in UAX#31, then we have at least one language-country pair in the LCPD.
3. If a language has a significant* literate population in a country, the pair is in the LCPD. This target is fuzzier, but definitely
   1. anything >1M, or
   2. >100K and either official (real, not honorary) or 1/3 of the population.

Implications for Likely Subtags

Likely Subtags are built from the language-country population data, plus the script metadata, plus an exception list.