EN 15907 Language Tag

From filmstandards.org

Definition from the standard

A coded value that may appear as an attribute or element value, denoting a natural language. The syntax for the language tag follows the definition given in RFC 4646. All codes from ISO 639-1and ISO 639-2 are syntactically valid RFC 4646 expressions. Therefore, all extensions such as script, region and language variant are optional.

EN 15907 Overview