17. The method according to claim 16 , wherein the determining the final domain comprises determining the candidate domain related to the first utterance element representing the user action from among the at least one candidate domain related to the detected expansion domain as the final domain, in response to determining that the detected candidate domain and the previous domain are different from each other or the context initialization has occurred.
18. The method according to claim 17 , wherein the determining the final domain comprises determining all the detected candidate domains as the final domain, in response to the detected candidate domain including main action information corresponding to the first utterance element representing the user action.