Figure 1(a) shows such an example, in which a development set contains two sentences f 1 and f 2 with translations e and feature vectors h. When we tune examples in Figure 1(a) by MERT, it can be regarded as a nonlinearly separable classification problem illustrated in Figure 1(b).
there exists no single weight W which simultaneously obtains e 11 and e 21 as translation for f 1 and f 2 via Equation (1).