A method includes: acquiring first voice information indicating a voice of a user input from a microphone; outputting, to a server via a network, first text string information generated from the first voice information, when the first text string information does not match any of pieces of text string information in the first database; acquiring, from the server, first semantic information and/or a control command corresponding to the first semantic information, when a second database includes a piece of text string information matched with the first text string information and the matched piece of text string information is associated with the first semantic information therein; instructing at least one device to execute an operation based on the first semantic information and/or the control command; and outputting, to a speaker, second voice information generated from second text string information, the second text string information being registered and associated with the first semantic information in the first database.