1. A method performed by data processing apparatus, the method comprising: determining, for each of a plurality of user devices, an answer box and subsequent query pair, wherein for each pair the answer box is provided to the user device for user consumption and the subsequent query is received from the user device subsequent to the answer box being received at the user device; for each pair of an answer box and a subsequent query determining whether the answer box includes attribute values for attributes that are predefined as being indicative of a discourse context, wherein a discourse context is a context in which content of an answer box is applicable to the subsequent query for generating a discourse query; for each subsequent query of a pair for which the answer box is determined to include attribute values for attributes that are predefined as being indicative of a discourse context, determining the subsequent query belongs to the discourse context when the subsequent query includes one or more terms that are pre-associated with the attributes of the answer box that are indicative of the discourse context; for each subsequent query of a pair determined to belong to a discourse context: generating a discourse query that is based on terms of the subsequent query and attribute values of the attributes of the answer box indicative of the discourse context; and providing the discourse query to a search engine so the search engine provides, to the user device that provided subsequent query, search results responsive to the discourse query in response to the subsequent query; and for each subsequent query of a pair for which the answer box is not determined to be indicative of the discourse context, and for each subsequent query of a pair for which the subsequent query is determined not to belong to the discourse context, providing the subsequent query to a search engine so the search engine provides, to the user device that provided the subsequent query, search results responsive to the subsequent query, and wherein at least one answer box is determined to not include attributes that are predefined as being indicative of a discourse context.