Marcos asked for a way to get the language of the current element. The DOM would define the concept and an attribute, HTML / XML would define its details. Robin suggested "baseLang" as attribute name.
*** Bug 21780 has been marked as a duplicate of this bug. ***
Considerations here are:
* xml:lang vs lang
* Whether lang needs to be superglobal
* Content-Language (see :lang())
Sufficient interest has not materialized.