Minimization algorithms for sequential transducers

We present general algorithms for minimizing sequential nite-state transducers that output strings or numbers. The algorithms are shown to be e cient since in the case of acyclic transducers and for output strings they operate in O(S + |E|+ |V |+ (|E| − |V |+ |F |) · (|Pmax|+ 1)) steps, where S is the sum of the lengths of all output labels of the resulting transducer, E the set of transitions of the given transducer, V the set of its states, F the set of nal states, and Pmax one of the longest of the longest common pre xes of the output paths leaving each state of the transducer. The algorithms apply to a larger class of transducers which includes subsequential transducers. c © 2000 Elsevier Science B.V. All rights reserved.