An aspect of the present invention simplifies development of user interfaces of applications. In one embodiment, specifications of user interfaces provided by applications are maintained, each specification containing interface definitions of UI elements in the corresponding user interface. A first user interface of a first application and a second user interface of a second application are displayed on a display unit. In response to receiving from a developer, an indication that a first UI element from the first user interface and a second UI element from the second user interface elements are to be included in a new user interface of a new application, a new specification for the new user interface incorporating the interface definitions of the first and second UI elements is created.