Two-stage MT systems have been proposed before [Xu and Seneff2008],
[Ehara2007], [Dugast
2007], [Simar
2007]. L. Dugast, et al. [Dugast
2007]
and M. Simard, et al. [Simar
2007] applied SYSTRAN and SMT for
Japanese-English translation. Their concept was to use SMT as a
post-process for SYSTRAN. The results of these studies indicated that
these systems are more effective than using SYSTRAN or SMT alone. In
M. Simard's research [Simar
2007], the BLEU score was 0.2598 for SMT
and 0.2880 for SYSTRAN + SMT in English-Japanese translation, and
0.2517 for SMT and 0.2679 for SYSTRAN + SMT in Japanese-English
translation. Ehara[Ehara2007] reported on the same system for
Japanese-English translation of a patent task. The BLEU score was
0.2821 for SMT and 0.2921 for RBMT + SMT. Ehara's RBMT system was a
commercial Japanese-English system. For these systems, SMT was used in
the post-process for RBMT, which means that SMT was used as a means of
language adaptation. Also, these RBMT systems were created by hand, so
they were expensive to build.