4. The method of claim 1 , wherein identifying a matching cluster, of the one or more previously generated clusters, with which the input question is associated comprises identifying a plurality of matching clusters with which the input question is associated, and wherein identifying a QA system pipeline associated with the matching cluster comprises identifying a plurality of QA system pipelines associated with the plurality of matching clusters.
5. The method of claim 4 , wherein processing, by the data processing system, the input question using the identified QA system pipeline to generate one or more candidate answers for the input question comprises generating, by each of the QA system pipelines associated with matching clusters in the plurality of clusters, a separate ranked listing of candidate answers.