Hereinafter, embodiments of a computer system to which a voice assistant system, a server apparatus, a device, a voice assistant method, and a program to be executed by a computer according to these embodiments are applied are described. Constituent components of some embodiments of the present invention are generally illustrated in the drawings of this specification but it can be easily understood that the constituent components may be variously disposed and designed with various configurations. Therefore, the following more detailed description about the apparatus, the method, and the program of some embodiments of the present invention does not limit the scope of embodiments of the present invention described in the Claims and merely describes examples of selected embodiments of the present invention and merely describes embodiments selected about the apparatus, the system, and the method without inconsistency with embodiments the present invention described in Claims of this specification. A person skilled in the art can understand that some embodiments of the present invention can be realized with the other methods, components, and materials, even in the absence of one or more of specific details.