Before revision:  In this paper, we pro-pose an approach to zero-shot learning (Xianet al., 2018) for ad-hoc retrieval models that relies on synthetic query generation . Crucially, the query generation system is trained on general domain data, but is applied to documents in the targeted domain.
After revision:  In this paper, we pro-pose an approach to zero-shot learning for passage retrieval that uses synthetic question generation to close this gap. The question generation system is trained on general domain data, but is applied to documents in the targeted domain.