1. A method of processing utterances, comprising: determining, for each of a plurality of time domains, if a significant word change has occurred within each of a plurality of utterances originating within a respective time domain; for each significant word change, identifying a word corresponding to each respective significant word change; generating, from the plurality of utterances, a first cluster of utterances including the word; and generating, from the plurality of utterances, a second cluster of utterances not including the word.