When the user says something on which the NLU is not trained, I want to categorize that as an ‘unknown’ intent. Is there a way to do that with Rasa?
I believe that issue is still somewhat open - https://github.com/RasaHQ/rasa_nlu/issues/387 . Note because it is a probabilistic system , anything that your system is not trained on will still get a probability. However see https://rasa.com/docs/core/fallbacks/ for an approach. Also https://blog.spg.ai/failing-gracefully-with-rasa-nlu-14a7d8e53af9 for some tips