The user interface layer consists of a Flex application, called the container application, that serves as a framework for a set of modular Flex elements. The container application supplies the structural components of the vSphere Web Client user interface, such as major navigation controls, window frames, and menus. The container application manages and renders each of the Flex GUI elements that it contains. Together, the collected Flex GUI elements and the container application make up the vSphere Web Client user interface.Each Flex GUI element inside the container application is a self-contained object that communicates directly with the vSphere environment. Each element can retrieve data for display, or send commands or make changes to the virtual infrastructure. Each GUI element implements a version of the MVC architecture to manage communication with the vSphere environment.The container application uses a metadata framework to determine where to place each GUI element in the interface, and how that element looks. Each GUI element has a metadata definition that you create using an XML schema that is defined in the vSphere Web Client SDK. The container application uses the values in the metadata definition to render the element at the appropriate place in the interface.