A system provides access to services from different servers via a common API. The system includes service-offering servers, a client that uses services offered by the service-offering servers, and an interchange server that acts as an intermediary when the client uses a service. The client communicates with the interchange server using a common API when the client uses service from the service-offering servers. The interchange server uses a unique API, which is unique to the service-offering server that offers the service being used by the client, to execute a processing sequence that is unique to the service-offering server. Thus client is able to use services offered by the service-offering servers with the use of a common API and without any need to use a different unique API for each service-offering server.