10. The method of claim 1 , wherein accessing data indicating the set of classes comprises accessing data indicating a hierarchy of classes corresponding to the particular semantic concept, wherein at least some of the classes in the hierarchy represent different forms of expressing at least a portion of the particular semantic concept.
10. The method of claim 1 , wherein accessing data indicating the set of classes comprises accessing data indicating a hierarchy of classes corresponding to the particular semantic concept, wherein at least some of the classes in the hierarchy represent different forms of expressing at least a portion of the particular semantic concept. 13. The method of claim 10 , further comprising: generating, for each additional set of classes in the hierarchy that represents the concept other than the first class and the multiple second classes, an additional language model in which the additional set of classes represents the concept; obtaining output of each of the additional language models for the set of input data; and evaluating the output of each of the additional language models; selecting one or more of the classes in the hierarchy of classes based on evaluating the output of the first language model and the output of the second language model and based on evaluating the output of each of the additional language models.