The present invention defines a method for assembling software components using an application controller. The application controller provides a conduit through which calling client modules can access functionality provided by various handlers in a manner that results in greater flexibility when additional functionality is required. Additional functionality can be provided to the clients by adding additional handlers to the application controller without the need to modify any of the individual clients. The client will continue invoking the application controller in the same manner as it did previously, whilst the application controller provides additional functionality by accessing the additional handlers. Indeed, the only changes that are required are to an agent, which in preferred embodiments includes a relatively straightforward to modify XML configuration file.