Before revision:  In this paper, we address a very challenging and previously underexplored version of this domain adaptation problem . In our setup an algorithm is trained on several source domains, and then applied to examples from an unseen domain that is unknown at training time.
After revision:  In this paper, we address a very challenging and previously underexplored version of this domain adaptation problem , where an algorithm is trained on several source domains, and then applied to examples from an unseen domain that is unknown at training time.