Unfortunately, the coherence assumption of the global approach does not hold in some situations, necessitating the discrete/coarse features in the local approach as a mechanism to compensate for the potential exceptions of the coherence assumption Hoffart et al., 2011;Sil et al., 2012;Durrett and Klein, 2014;Pershina et al., 2015).
the global approach is still subject to the second limitation of data sparseness of the local approach due to their use of discrete features.