Earlier systems of this type comprise various modules such as, for example, query reformulation (e. g., Brill et al., 2002), question classification (Li and Roth, 2006), passage retrieval (e. g., Harabagiu et al., 2000), or answer extraction (Shen and Klakow, 2006).
the aforementioned modules have been reduced to two consecutive steps with the advent of neural QA.