I am trying to apply a rule on a boolean type attribute to find if the value is “Ja” or "Nee”. However I couldn’t  achieve the expected outcome with advanced expression as its a bolean type. Also looked in to the documentation for one expression.
Any suggestions to get the similar results with boolean type attribute?
Best answer by matej
Not sure if I understand the question properly @Gerson, however:
If you are trying to check if the values of the column contains only either “Ja” or “Nee”, then this Advanced Expression should work for you:
(INPUT is in {"Ja", "Nee"})
If the column doesn’t contain strings “Ja” or “Nee”, but rather values expressing logical TRUE and FALSE (column of a boolean type), then this should work for you:
Not sure if I understand the question properly @Gerson, however:
If you are trying to check if the values of the column contains only either “Ja” or “Nee”, then this Advanced Expression should work for you:
(INPUT is in {"Ja", "Nee"})
If the column doesn’t contain strings “Ja” or “Nee”, but rather values expressing logical TRUE and FALSE (column of a boolean type), then this should work for you: