“…Post-retrieval QPP features have been found to be more effective that pre-retrieval features, although they are much more expensive to calculate, as they need the IR system to run the query in order to make the prediction. While the first studies on QPP used single features [2,3,4,5,6], a more recent path is to combine various query features [7,4,8,9,10]. While combining multiple post-retrieval features improves accuracy, the method becomes applicable in real-world scenarios only if the number of features is limited to just a few, due to the increased computational time required for obtaining these features.…”