19. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: while receiving a first text input entered in a search engine query input field by a first user, and before the first user has submitted the first text input as a search request: deriving, in a data processing system, a first dominant query from the first text input, wherein deriving the first dominant query includes: determining that the first text input is missing information needed to trigger an answer box; obtaining the needed information from user profile data for the first user, including analyzing the user profile data for the first user to determine that a particular category of answer box is relevant to the first user; and generating the first dominant query from the first text input, the needed information, and the particular category of answer box; obtaining, by the system, content for a first answer box associated with the first dominant query; and presenting the first answer box to the first user.
19. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: while receiving a first text input entered in a search engine query input field by a first user, and before the first user has submitted the first text input as a search request: deriving, in a data processing system, a first dominant query from the first text input, wherein deriving the first dominant query includes: determining that the first text input is missing information needed to trigger an answer box; obtaining the needed information from user profile data for the first user, including analyzing the user profile data for the first user to determine that a particular category of answer box is relevant to the first user; and generating the first dominant query from the first text input, the needed information, and the particular category of answer box; obtaining, by the system, content for a first answer box associated with the first dominant query; and presenting the first answer box to the first user. 20. The system of claim 19 , wherein generating the first dominant query includes: receiving a group of queries including one or more query suggestions for the first text input; determining a popularity value for each query in the group of queries, the popularity value for each query being derived from a number of times one or more users submitted the query suggestion; and identifying a selected query from the one or more queries as the first dominant query, the selected query having a popularity value that exceeds a threshold.