The eXpressApp Framework automatically generates the UI based on your business model. This UI contains built-in features to work with data: filtering, reporting, navigating and so on. These features may be sufficient for a simple business application. However, complex applications may demand a more extensive functionality set. To implement additional features, the eXpressApp Framework provides the Controllers and Actions concept. This concept allows the implementation of both internal application features and end-user interaction. Topics in this section will familiarize you with these concepts, and enable you to use them in your applications.