1. A method of simplifying development of user interfaces of applications, said method comprising: maintaining a plurality of specifications of user interfaces provided by a plurality of applications, each of said plurality of specifications containing interface definitions of a corresponding set of UI elements in the respective user interface; displaying on a display unit, a first user interface of a first application and a second user interface of a second application, said first user interface having a first set of UI elements and said second user interface having a second set of UI elements, said first application and said second application being contained in said plurality of applications; receiving, from a developer, an indication that a first UI element from said first set of UI elements and a second UI element from said second set of UI elements are to be included in a new user interface of a new application; and creating a new specification for said new user interface incorporating the interface definitions of said first UI element and said second UI element, the interface definitions of said first UI element and said second UI element being retrieved respectively from a first specification and a second specification of said plurality of specifications.