Synchronization

Operations such as composition are defined for pfst. Therefore, we have implemented an operator which transforms a given bounded qpfst back into pfst by synchronizing the identities. Of course, the resulting pfst will generally not be deterministic anymore.

The synchronization is implemented by an algorithm which maintains an agenda of `synchronous states' (initialized by the set of start states). For each state on the agenda minimal synchronous paths are generated. The target states of these paths are added to the agenda, and these paths themselves are broken into pieces such that each piece is synchronous (by introducing transitions with $\epsilon$ on the input or output side).