15. The system of claim 9 , wherein the first case comprises at least one question presented to the question answering system.
15. The system of claim 9 , wherein the first case comprises at least one question presented to the question answering system. 16. The system of claim 15 , wherein the first feature comprises at least one of: (i) a type, (ii) a subject matter, (iii) a variable, and (iv) a context of the at least one question.