6. The method of claim 5 further comprising steps for, prior to evaluating the user query to identify one or more subqueries, checking the reformulation cache to determine whether the current user query has been previously reformulated, and if so, using the corresponding reformulated query from the reformulation cache to retrieve and present the set of ranked search results without identifying subqueries and retrieving partial answers for subqueries.
5. The method of claim 1 further comprising steps for providing a historical “reformulation cache” comprising a plurality of reformulated queries constructed from prior user queries of a plurality of users.