1. A call center device operating in conjunction with a telephonic or online chat communication station, the call center device comprising: a dialog manager configured to determine a recommended agent dialog act based on past dialog between a call center agent and a second party which is received from the telephonic or online chat communication station; and an utterance generation component configured to generate at least one recommended agent utterance for implementing the recommended dialog act by operations including: ranking a set of word lattices each represented as a weighted finite state automaton (WFSA) by conditional probabilities p(τ|DA type) where τ is a word lattice and DA type is a dialog act type of the recommended dialog act, choosing at least one word lattice from the ranking, and instantiating the chosen at least one word lattice to generate the at least one recommended agent utterance; wherein the dialog manager and the utterance generation component comprise at least one computer programmed to determine the recommended dialog act and to generate the at least one recommended agent utterance.