A system makes it possible to use services offered by a plurality of servers different from one another is realized with the use of a common API. The system includes a plurality of service-offering servers, a client that uses services offered by the plurality of service-offering servers, and an interchange server that performs intermediary processing when the client uses a service. The client performs communication with the interchange server while using a common API when using any service among a plurality of services offered by the plurality of service-offering servers. The interchange server uses a unique API, which is unique to the service-offering server that offers the service selected by the client, to execute a processing sequence that is unique to the service-offering server. The client may use any service among services offered by the plurality of service-offering servers with the use of a common API without any need to use a unique API, which is unique to each of the plurality of service-offering servers.