11. The system of claim 10 , the preference component includes a model where a user assesses a parameter v, indicating a dollar value of receiving a correct answer to a question, and where a parameter c represents a cost of each query rewrite submitted to a search engine.
11. The system of claim 10 , the preference component includes a model where a user assesses a parameter v, indicating a dollar value of receiving a correct answer to a question, and where a parameter c represents a cost of each query rewrite submitted to a search engine. 12. The system of claim 11 , further comprising a value of receiving an answer expressed as a function of details of a current context, the value of the answer is linked to at least one of a type of question, an informational goal, or a time of day for a user.