“…Second, this interaction is expected to happen in a natural way, adapted to the characteristics of the situation, the user preferences and abilities, the environment characteristics, and the interactive devices available in each location. For this reason, in Ubiquitous Computing, Windows, Icons, Menus, Pointer (WIMP) user interfaces are the exception, and Natural User Interfaces (NUIs) implemented with Physical User Interfaces (PUIs) are the norm [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. Last, but not least, UC systems are expected to be ubiquitous or, at least, to seem ubiquitous, by providing their functionalities in many places.…”