System combination has also been successfully applied to statistical machine translation system (SMT) (Och and Ney, 2001;Matusov et al., 2006;Schwartz, 2008;Schroeder et al., 2009).
system combination methods in the phrase-based (PBSMT) (Koehn et al., 2003) and hierarchical (HSMT) frameworks (Chiang, 2007) tend to be rather complex, requiring potentially non-trivial mappings between the partial hypotheses across the search spaces of the individual systems.