Systems and techniques that provide improvements to designer applications as described to address, for example, limitations associated with constructing a user interface as it is being designed by a user in a development environment. In some implementations, a system provides a design interface through which a user can view, develop, and test functional aspects of an electronic form in real-time while the user is building the application. The system maintains associations between components of the electronic form and expressions for the components referenced in program logic for the electronic form.