Most of the extensions of ROVER, such as iROVER (Hillard et al., 2007), cROVER (Abida et al., 2011) and the one described in (Zhang and Rudnicky, 2006), aim to learn a scoring function that allows improving the reordering of words inside each slot.
iROVER reorders the words in each slot by means of a classifier trained with features that characterize the individual ASR systems.