Human and device objects of the physical layer can access applications of the DMH through a unified access interface mechanism. As explained earlier, the software architecture of this hub follows the MVC pattern in which the controller and view of all applications are represented by a core functionality module called service request manager, as shown in Fig. 4. The controller handles all business logic processes including virtualization of POs, interactions between VOs, and performs all tasks relevant to service creation and management. It also acts as a coordinator between the models and views for nonAsynchronous JavaScript and XML (AJAX) requests (i.e. first page loading) of the browser-based interface. All subsequent AJAX requests are handled by the unified access interface. This saves processing time, minimizes page-loading time, and thus improves the user-machine interactivity.