The DATEX-definition for the attribute "defaultLanguage" is
"The default language used throughout the payload publications, specified by an ISO 639-2 3-alpha code." and similar for "language" of MultilingualStrings. In our perception, this definition is ignored, and usually the two-alpha code instead of the three-alpha code is used (even in the XML-examples on the website). The internal UML schema "language" does allow both variants. Proposal: Change definition(s) to ISO 639-1 two-alpha code (or maybe allow usage of both variants).
The definitions of the defaultLanguage attribute has been amended to “The default language used throughout the payload publication.” and that of datatype Language to “A language datatype, identifies a specified language by an ISO 639-1 2-alpha / ISO 639-2 3-alpha code.”