The base language under which this resource should be processed.

This is not necessarily the same as the language of the resource itself; for example, a French phrase in an English dictionary might be in the French language, but processed under English processing rules (for alphebetization, ⁊·c).

only specifies the range of this property as , but it then additionally requires that it match the expectations of . As these datatypes share a value space, it is simpler to just use the latter as its range.