Some embodiments provide a non-transitory machine-readable medium that stores a program. The program receives a request for questions associated with a location and a category. The program also identifies a matrix, a hierarchy of locations associated with the matrix, and a hierarchy of categories associated with the matrix. The program further determines an aggregate collection of questions from a plurality of sets of questions based on the matrix, the hierarchy of locations, and the hierarchy of categories. The program also generates the aggregate collection of questions.