5. A computer-implemented method comprising: under control of one or more computing devices configured with specific computer-executable instructions, generating a transcription of at least a portion of an utterance, wherein the transcription comprises a sequence of tokens corresponding to at least a portion of a search query; identifying a first subset of the sequence of tokens as a reference to an entity in the transcription based at least partly on a first frequency with which at least a first token of the first subset occurs in a plurality of previously submitted search queries; identifying a second subset of the sequence of tokens as a reference to an attribute of the entity in the transcription based at least partly on a second frequency with which at least a second token of the second subset occurs with the first token in the plurality of previously submitted search queries, wherein the second token occurring with the first token comprises the second token and first token both occurring in a same search query of the plurality of previously submitted search queries; generating search terms using the reference to the entity and the reference to the attribute, wherein the search terms include the first subset and second subset, and wherein the search terms exclude a third subset of the sequence of tokens; and generating search results responsive to the search query by identifying an item in a product catalog using the search terms, wherein the product catalog indicates the item comprises an instance of the entity having the attribute.
5. A computer-implemented method comprising: under control of one or more computing devices configured with specific computer-executable instructions, generating a transcription of at least a portion of an utterance, wherein the transcription comprises a sequence of tokens corresponding to at least a portion of a search query; identifying a first subset of the sequence of tokens as a reference to an entity in the transcription based at least partly on a first frequency with which at least a first token of the first subset occurs in a plurality of previously submitted search queries; identifying a second subset of the sequence of tokens as a reference to an attribute of the entity in the transcription based at least partly on a second frequency with which at least a second token of the second subset occurs with the first token in the plurality of previously submitted search queries, wherein the second token occurring with the first token comprises the second token and first token both occurring in a same search query of the plurality of previously submitted search queries; generating search terms using the reference to the entity and the reference to the attribute, wherein the search terms include the first subset and second subset, and wherein the search terms exclude a third subset of the sequence of tokens; and generating search results responsive to the search query by identifying an item in a product catalog using the search terms, wherein the product catalog indicates the item comprises an instance of the entity having the attribute. 8. The computer-implemented method of claim 5 , wherein the entity comprises a named entity, and wherein the item identified in the product catalog is associated with a category corresponding to the named entity.