1. A system comprising: one or more processors; and computer-readable media having instructions that, when executed by the one or more processors, configure the one or more processors to perform operations comprising: generating signals representing a first weighted finite-state transducer (WFST); generating signals representing a second WFST; composing the first WFST and the second WFST to form a non-determinizable third WFST; and applying a determinization process to the non-determinizable third WFST to produce a non-fully deterministic fourth WFST.