Semi-supervised approaches for NMT are often based on automatically creating pseudoparallel sentences through methods such as backtranslation (Irvine and Callison-Burch, 2013;Sennrich et al., 2016) or adding an auxiliary autoencoding task on monolingual data (Cheng et al., 2016;Currey et al., 2017).
both methods have problems with lowresource and syntactically divergent language pairs.