7. A system, comprising: one or more computer processors; and a memory containing a program, which, when executed by the one or more computer processors, performs an operation to identify features by a question answering system, the operation comprising: classifying a first case received by the question answering system as being of a first type; and training the question answering system to generate a response to the first case, wherein the training comprises: identifying a first feature and a second feature of the first case, wherein the first and second features comprise a first and a second variable of the first case, respectively; determining that the question answering system identified evidence while generating the response to the first case based on the first and second features of the first case; identifying a set of possible values for the first and second variables in the identified evidence, wherein the set of possible values for the first and second variables include: (i) a first value comprising reference value for the respective variables, (ii) a second value comprising an actual value for the respective variables, and (iii) a third value comprising an opinion value for the respective variables; determining that the question answering system generated the response to the first case based on the identified evidence and a weight applied to a combined feature comprising the first and second features, wherein the weight is of a range of weights applied by the question answering system to the combined feature; computing a first feature score for the combined feature, wherein the first feature score indicates the weight applied by the question answering system to the combined feature and the sets of possible values for the first and second variables when generating the response to the first case; and storing an indication of a relationship between the first feature, the second feature, the combined feature, the identified evidence, and cases classified as being of the first type upon determining that the first feature score exceeds a threshold, wherein the relationship reflects the weight applied to the combined feature when generating responses to cases classified as being of the first type.
7. A system, comprising: one or more computer processors; and a memory containing a program, which, when executed by the one or more computer processors, performs an operation to identify features by a question answering system, the operation comprising: classifying a first case received by the question answering system as being of a first type; and training the question answering system to generate a response to the first case, wherein the training comprises: identifying a first feature and a second feature of the first case, wherein the first and second features comprise a first and a second variable of the first case, respectively; determining that the question answering system identified evidence while generating the response to the first case based on the first and second features of the first case; identifying a set of possible values for the first and second variables in the identified evidence, wherein the set of possible values for the first and second variables include: (i) a first value comprising reference value for the respective variables, (ii) a second value comprising an actual value for the respective variables, and (iii) a third value comprising an opinion value for the respective variables; determining that the question answering system generated the response to the first case based on the identified evidence and a weight applied to a combined feature comprising the first and second features, wherein the weight is of a range of weights applied by the question answering system to the combined feature; computing a first feature score for the combined feature, wherein the first feature score indicates the weight applied by the question answering system to the combined feature and the sets of possible values for the first and second variables when generating the response to the first case; and storing an indication of a relationship between the first feature, the second feature, the combined feature, the identified evidence, and cases classified as being of the first type upon determining that the first feature score exceeds a threshold, wherein the relationship reflects the weight applied to the combined feature when generating responses to cases classified as being of the first type. 13. The system of claim 7 , wherein the first feature score is further based on a number of relevant items of supporting evidence retrieved by the question answering system using the first and second features.