As an RDF consumer (linked data interface, query service, or dumps), I want to work with standard language codes, not custom MediaWiki ones.
**Problem:**
We currently directly export the internal language codes to RDF (in terms and monolingual text): `simple` instead of `en-simple`, `de-formal` instead of `de-x-formal`, etc.
Note that we //do// map the language codes already for sitelinks (`schema:inLanguage`, `schema:name`).
**Example:**
The [sandbox item](https://www.wikidata.org/wiki/Q4115189) currently has a label in “de-formal”; to [this query](https://query.wikidata.org/#SELECT%20%3Flabel%20%28LANG%28%3Flabel%29%20AS%20%3Flang%29%20WHERE%20%7B%0A%20%20wd%3AQ4115189%20rdfs%3Alabel%20%3Flabel.%0A%20%20FILTER%28LANG%28%3Flabel%29%20IN%20%28%22de-formal%22%2C%20%22de-x-formal%22%29%29%0A%7D), that should appear as “de-x-formal”, but currently it doesn’t.
**Screenshots/mockups:**
**BDD**
GIVEN
AND
WHEN
AND
THEN
AND
**Acceptance criteria:**
* the language tag of labels, descriptions and aliases uses standard language codes
* the language tag of monolingual text values uses standard language codes
* the language tag of the `schema:name` of a sitelink uses standard language codes (already the case, should not regress)
* the `schema:inLanguage` of a sitelink uses standard language codes (already the case, should not regress)
**Open questions:**