We describe a lattice generation method that is exact, i.e. it satisfies all the natural properties we would want from a lattice of alternative transcriptions of an utterance. This method does not introduce substantial overhead above one-best decoding. Our method is most directly applicable when using WFST decoders where the WFST is “fully expanded”, i.e. where the arcs correspond to HMM transitions. It outputs lattices that include HMM-state-level alignments as well as word labels. The general idea is to create a state-level lattice during decoding, and to do a special form of determinization that retains only the best-scoring path for each word sequence. This special determinization algorithm is a solution to the following problem: Given a WFST A, compute a WFST B that, for each input-symbol sequence of A, contains just the lowest-cost path through A.

}, author = {Daniel Povey and Mirko Hannemann and Gilles Boulianne and Lukas Burget and Arnab Ghoshal and Milos Janda and Martin Karafiat and Stefan Kombrink and Petr Motlıcek and Yanmin Qian and Korbinian Riedhammer and Karel Vesely and Ngoc Thang Vu}, month = {March}, publisher = {IEEE International Confrence on Acoustics, Speech, and Signal Processing (ICASSP)}, title = {Generating Exact Lattices in the WFST Framework}, url = {http://research.microsoft.com/apps/pubs/default.aspx?id=164612}, year = {2012}, }