1. A system for developing a graphical user interface (GUI) for an enterprise business application using a model driven technique, the system comprising: a repository to store common structural elements, variable structural elements, variation points, behavioral variants and situation specific structural variants; and a processor coupled to the repository, wherein the processor executes program instructions to: model one or more screens on a presentation layer of the enterprise business application for facilitating user interaction, wherein the one or more screens are connected to one another by navigation links and are modeled according to a plurality of metamodels defined according to the enterprise business application, wherein the navigation links facilitate a user to navigate from an existing screen to a new screen of the one or more screens, wherein the existing screen comprises common structural elements and variable structural elements, and wherein the existing screen is modeled by specifying behavioral specification for the existing screen, wherein behavioral specification are defined by existing event handlers, wherein the existing event handlers execute events, wherein the new screen is modeled using the existing screen by: defining variation points on the existing screen, wherein the variation points are indicative of a position on the existing screen to define the behavioral variants or the situation specific structural variants, and wherein the variation points are defined by introducing a variable field widget, wherein the variable field widget is configured to indicate a place-holder in the existing screen for accommodating the behavioral variants or the situation specific structural variants; defining behavioral variants for the variation points on the existing screen, wherein the behavioral variants are defined by adding new event handlers or by overriding the existing event handlers, wherein the behavioral variants depend upon a metamodel of the plurality of metamodels for specifying behavioral variations of the new screen, wherein the metamodel is defined for the new screen, wherein event handlers are configured to invoke services, trigger navigations or execute code specified by the user; defining situation specific structural variants at the variation points on the existing screen to specify structural extensions to the existing screen, wherein the situation specific structural variation correspond to structural variations for the new screen depending upon the metamodel defined for the new screen, wherein the situation specific structural variants are defined by introducing new structural elements onto the existing screen or by overriding the variable structural elements, wherein the situation specific structural variants correspond to a new widget to be added to the existing screen, or a changing the type of an existing widgets associated with the existing screen; and deriving specifications of the GUI of the new screen using the behavioral variants and the situation specific structural variants.