A model for the development of computing in the early 21st century. It envisages a movement away from ‘computers’ as distinct specialized devices; rather, many objects used in everyday life will contain embedded computing devices that can recognize and interact in useful ways with each other and with their environment. Commonly cited examples are the refrigerator that is aware of its contents via embedded tags and is thus able to suggest shopping lists, plan menus, warn of approaching expiry dates, etc.; a home environment (heating, lighting, etc.) that continuously adjusts itself according to data from biometric monitors incorporated into clothing; and automatic recognition of a returning home owner so that security alarms are switched off and appropriate in-house systems activated. Such a model becomes possible as the size of computing devices decreases and their power increases, with wireless networking making the ad-hoc self-configuring networks necessary for ubiquitous computing viable (see Bluetooth). A key issue is how humans interact with such a system. The ideal is that such interaction should be unobtrusive and natural for the user, emphasizing speech recognition and artificial intelligence. Another issue is privacy: a truly useful ubiquitous computing system will inevitably acquire a large amount of personal data about its users. Ubiquitous computing is currently a subject of both academic and commercial research.