5. The method of claim 3 , wherein selecting, using the probabilistic model, one or more states that are likely to generate the set of words comprises: selecting, for the probabilistic model, a starting state, wherein the starting state identifies nodes in the probabilistic model as being active or inactive; and determining, using the starting state, one or more states that are likely to generate the set of words, the one or more states having been determined based on a hill climbing operation.
6. The method of claim 5 , wherein the nodes in the probabilistic model comprise one or more clusters that correspond to the set of words and one or more terminal nodes that correspond to the set of words.