Given a group of WFSTs, each of which models a stage of a mapping cascade, the composition operation provides an efficient approach to combine them into a single one (Mohri et al., 2002;Mohri et al., 1996).
in (Takaaki Hori and Minami, 2003), the WFST has been further used for language model adaptation, where language models of different vocabularies that represented different styles were integrated through the framework of speech translation.