Task: Question Answering
Input (English): Our goal is to decouple the content selection from the decoder by introducing an extra content selector. The most intuitive way is training the content selector to target some heuristically extracted contents. For example, we can train the selector to select overlapped words between the source and target BIBREF6 , sentences with higher tf-idf scores BIBREF20 or identified image objects that appear in the caption BIBREF21 . INLINEFORM0 as Latent Variable: Another way is to treat INLINEFORM1 as a latent variable and co-train selector and generator by maximizing the marginal data likelihood. By doing so, the selector has the potential to automatically explore optimal selecting strategies best fit for the corresponding generator component. Reinforce-select (RS) BIBREF24 , BIBREF9 utilizes reinforcement learning to approximate the marginal likelihood. We propose Variational Reinforce-Select (VRS) which applies variational inference BIBREF10 for variance reduction. 
 Question: How is the model trained to do only content selection?
Output (English): target some heuristically extracted contents treat INLINEFORM1 as a latent variable and co-train selector and generator by maximizing the marginal data likelihood reinforcement learning to approximate the marginal likelihood  Variational Reinforce-Select (VRS) which applies variational inference BIBREF10 for variance reduction