31. A query system, comprising: a query receiver which receives a user query; a semantic analyzing device which parses the user query and semantically analyzes the user query; a determining device which determines whether the user query is a complete user query; a first service selecting device which performs a process on the complete user query and selects a first selected service from among a plurality of services based on the complete user query; a second service selecting device which complements an incomplete user query to complete the incomplete user query and selects a second selected service from among the plurality of services based on the completed incomplete user query; a retrieving device which retrieves an answer according to the first selected service or the second selected service; an answer sender which sends the answer to a user; and at least one processor coupled to the query receiver, the semantic analyzing device, the determining device, the first service selecting device, the second service selecting device, the retrieving device and the answer sender, wherein the second service selecting device comprises a semi-automatic service selecting section which searches lost content in the incomplete query by using a service mapping rule base and complements the lost content through an interacting with the user, wherein the semi-automatic service selecting section comprises: a lost content searching unit which matches the semantically-analyzed query with a service mapping rule in the service mapping rule base, and extracts a service type to which the incomplete query belongs and a lost parameter in the incomplete query; a user interacting unit which prompts the user to input prompt information of a parameter value corresponding to the lost parameter and receives feedback information including the parameter value from the user; a parameter value extracting unit which extracts the parameter value from the feedback information of the user; and a query complementing unit which adds the service type, the lost parameter and the parameter value into the semantically-analyzed query to form the complete query.
32. The query system according to claim 31 , wherein the determining device matches the semantically-analyzed user query with the service mapping rule in the service mapping rule base, if a matching is successful, the user query is sent to the first service selecting device; and if the matching is not successful, the user query is sent to the second service selecting device.