Ubiquitous computing (pervasive) is a concept in software engineering and computer science where computing is made to appear everywhere and anywhere. In contrast to desktop computing, ubiquitous computing can occur using any device, in any location, and in any format. A user interacts with the computer, which can exist in many different forms, including laptop computers, tablets and terminals in everyday objects such as a fridge or a pair of glasses. The underlying technologies to support ubiquitous computing include Internet, advanced middleware, operating system, mobile code, sensors, microprocessors, new I/O and user interfaces, networks, mobile protocols, location and positioning and new materials.

 This new paradigm is also described as pervasive computing, ambient intelligence, or ‘every ware’. Each term emphasizes slightly different aspects. When primarily concerning the objects involved, it is also known as physical computing, the Internet of Things, hap tic computing, and ‘things that think’. Rather than propose a single definition for ubiquitous computing and for these related terms, taxonomy of properties for ubiquitous computing has been proposed, from which different kinds or flavors of ubiquitous systems and applications can be described.

Ubiquitous computing touches on a wide range of research topics, including distributed computing, mobile computing, location computing, mobile networking, context-aware computing, sensor networks, human-computer interaction, and artificial intelligence.

  Core concepts

             At their core, all models of ubiquitous computing share a vision of small, inexpensive, robust networked processing devices, distributed at all scales throughout everyday life and generally turned to distinctly common-place ends. For example, a domestic ubiquitous computing environment might interconnect lighting and environmental controls with personal biometric monitors woven into clothing so that illumination and heating conditions in a room might be modulated, continuously and imperceptibly. Another common scenario posits refrigerators “aware” of their suitably tagged contents, able to both plan a variety of menus from the food actually on hand, and warn users of stale or spoiled food.

            Ubiquitous computing presents challenges across computer science: in systems design and engineering, in systems modeling, and in user interface design. Contemporary human-computer interaction models, whether command-line, menu-driven, or GUI-based, are inappropriate and inadequate to the ubiquitous case. This suggests that the “natural” interaction paradigm appropriate to a fully robust ubiquitous computing has yet to emerge – although there is also recognition in the field that in many ways we are already living in an ubicomp world (see also the main article on Natural User Interface). Contemporary devices that lend some support to this latter idea include mobile phones, digital audio players, radio-frequency identification tags, GPS, and interactive whiteboards.

                         Mark Weiser proposed three basic forms for ubiquitous system devices: tabs, pads and boards.

                              Tabs: wearable centimetre sized devices

                              Pads: hand-held decimetre-sized devices

                              Boards: metre sized interactive display devices.

                         These three forms proposed by Weiser are characterized by being macro-sized, having a planar form and on incorporating visual output displays. If we relax each of these three characteristics we can expand this range into a much more diverse and potentially more useful range of Ubiquitous Computing devices. Hence, three additional forms for ubiquitous systems have been proposed:

                              Dust: miniaturized devices can be without visual output displays, e.g. Micro Electro-Mechanical Systems (MEMS), ranging from nanometres through micrometers to millimetres. See also Smart dust.

                              Skin: fabrics based upon light emitting and conductive polymers, organic computer devices, can be formed into more flexible non-planar display surfaces and products such as clothes and curtains, see OLED display. MEMS device can also be painted onto various surfaces so that a variety of physical world structures can act as networked surfaces of MEMS.

                              Clay: ensembles of MEMS can be formed into arbitrary three dimensional shapes as artifacts resembling many different kinds of physical object (see also Tangible interface).

                         In his book The Rise of the Network Society, Manuel Castells suggests that there is an ongoing shift from already-decentralized, stand-alone microcomputers and mainframes towards entirely pervasive computing. In his model of a pervasive computing system, Castells uses the example of the Internet as the start of a pervasive computing system. The logical progression from that paradigm is a system where that networking logic becomes applicable in every realm of daily activity, in every location and every context. Castells envisages a system where billions of miniature, ubiquitous inter-communication devices will be spread worldwide, “like pigment in the wall paint”.

                         Ubiquitous computing may be seen to consist of many layers, each with their own roles, which together form a single system:

                         Layer 1: task management layer

                              Monitors user task, context and index

                              Map user’s task to need for the services in the environment

                              To manage complex dependencies

                         Layer 2: environment management layer

                              To monitor a resource and its capabilities

                              To map service need, user level states of specific capabilities

                         Layer 3: environment layer

                              To monitor a relevant resource

                              To manage reliability of the resources