i18n-translation pepending on document language

Hello developers

Is it possible to translate specific strings by the help of the Five 
machinery depending on the document's language setting. The standard 
i18n procedure for Silva is targeted mainly at the translation of the 
SMI. In my case, I would like to translate the label of a forms button 
in a Silva extension which shows up on public pages. In this case it 
makes more sense to set the language to the document's language rather 
than the user preferences (set in either Silva's user settings or the 
user's browser setting). This translation might be performed in a Python 
Script.

Any ideas?

Regards
Sam