6. A computer system for semantic classification, the computer system comprising: a processor; and a memory coupled to the processor, the memory storing instructions that when executed by the processor cause the system to perform the operations of: receiving a first utterance for use in training a first automatic semantic classifier, the first automatic semantic classifier having a set of semantic classes for labeling transcribed utterances, the first utterance being a transcribed utterance classified in a first semantic class within the set of semantic classes; semantically labeling the first utterance using a second automatic semantic classifier, the second automatic semantic classifier being a previously-trained semantic classifier; semantically labeling existing utterances using the second automatic semantic classifier, the existing utterances accessed from a database of existing utterances, the database of existing utterances containing transcribed utterances used to train previously-trained automatic semantic classifiers; identifying existing utterances that are semantically similar to the first utterance based on semantic labeling from the second automatic classifier; and training the first automatic semantic classifier using the semantically similar existing utterances.
6. A computer system for semantic classification, the computer system comprising: a processor; and a memory coupled to the processor, the memory storing instructions that when executed by the processor cause the system to perform the operations of: receiving a first utterance for use in training a first automatic semantic classifier, the first automatic semantic classifier having a set of semantic classes for labeling transcribed utterances, the first utterance being a transcribed utterance classified in a first semantic class within the set of semantic classes; semantically labeling the first utterance using a second automatic semantic classifier, the second automatic semantic classifier being a previously-trained semantic classifier; semantically labeling existing utterances using the second automatic semantic classifier, the existing utterances accessed from a database of existing utterances, the database of existing utterances containing transcribed utterances used to train previously-trained automatic semantic classifiers; identifying existing utterances that are semantically similar to the first utterance based on semantic labeling from the second automatic classifier; and training the first automatic semantic classifier using the semantically similar existing utterances. 7. The computer system of claim 6 , wherein the memory stores further instructions that when executed by the processor cause the system to perform the operations of: semantically labeling the first utterance using multiple automatic semantic classifiers, the multiple automatic semantic classifiers being previously-trained semantic classifiers, wherein each of the multiple automatic semantic classifiers separately labels the first utterance; and semantically labeling the existing utterances using the multiple automatic semantic classifiers, wherein each of the multiple automatic semantic classifiers separately labels the existing utterances.