A system for extending an enterprise resource planning application is provided. The system employs “Add-ins” that each have a functional behavior that is independent of the client on which it executes and a user interface behavior that is dependent on the characteristics of the display, and other characteristics, of the client (i.e., a display target). When a user attempts to invoke an Add-in via the client runtime, the client runtime determines whether the Add-in is available at the user's computer. If not, the client runtime downloads the appropriate artifact for execution at the user's computer. In this environment, neither the client runtime nor the server-side business logic contains the logic used to implement a particular Add-in behavior on the supported display targets. Instead, this logic is contained within separate artifacts associated with a single Add-in having a particular behavior, each artifact implementing the behavior for a specific display target.