6. The method of claim 1 , further comprising: identifying a second variable in the source code of the QA system; determining that a weight applied to a value of the second variable by a second rule in the source code increases the confidence score for candidate answers generated by the QA system beyond the threshold; computing an influence score for the second variable based on the weight applied to the value of the second variable by the second rule in the source code; computing an importance score for the second variable based at least in part on the computed influence score for the second variable; and determining that the importance score exceeds the predefined threshold.
7. The method of claim 6 , further comprising: receiving, by the QA system, a case that does not specify values for at least the first and second variables; determining that the importance score for the first variable is greater than the importance for the second variable; and outputting, to a user, a request to provide values for the first and second variables, wherein the request is ordered based on the importance score of the first variable being greater than the importance score of the second variable.