18. The computer storage medium of claim 16 , wherein determining that the first search query includes a respective text reference to each of one or more predetermined attributes comprises: determining, only from text of the search query, that the first search query includes a respective text reference to each of one or more predetermined attributes.
16. A computer storage medium encoded with a computer program, the program comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising: determining that a first search query includes a respective text reference to each of one or more predetermined attributes, wherein each attribute is associated with a first entity type; generating a second search query including the first search query and one or more terms that refer to the first entity type; and evaluating search results obtained for the second search query to select one or more names of entities of the first entity type to include in a response to the first search query, wherein each search result identifies a respective search result resource, and wherein evaluating the search results comprises: identifying occurrences of references to entities of the first entity type in the same search result resource as one or more terms from the first search query; and selecting the names of entities based on the identified occurrences.