Ubiquitous computing (ubicomp) is a post-desktop model of human-computer interaction in which information processing has been thoroughly integrated into everyday objects and activities.
In the course of ordinary activities, someone "using" ubiquitous computing engages some computational devices and systems simultaneously, and may not necessarily even be aware that they are doing so. This model is considered an advancement from the older desktop paradigm. More formally, ubiquitous computing is defined as "machines that fit the human environment instead of forcing humans to enter theirs".
This paradigm is also described as pervasive computing, ambient intelligence, or, more recently, everyware, where each term emphasizes slightly different aspects. When primarily concerning the objects involved, it is also physical computing, the Internet of Things, haptic computing, and things that think. Rather than propose a single definition for ubiquitous computing and for these related terms, a taxonomy of properties for ubiquitous computing has been proposed, from which different kinds or flavors of ubiquitous systems and applications can be described.
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 modelling, 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. Contemporary devices that lend some support to this latter idea include mobile phones, digital audio players, radio-frequency identification tags, GPS, and interactive whiteboards.
- 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 artefacts 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-decentralised, 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
Mark Weiser coined the phrase "ubiquitous computing" around 1988, during his tenure as Chief Technologist of the Xerox Palo Alto Research Center (PARC). Both alone and with PARC Director and Chief Scientist John Seely Brown, Weiser wrote some of the earliest papers on the subject, largely defining it and sketching out its major concerns.
Recognizing that the extension of processing power into everyday scenarios would necessitate understandings of social, cultural and psychological phenomena beyond its proper ambit, Weiser was influenced by many fields outside computer science, including "philosophy, phenomenology, anthropology, psychology, post-Modernism, sociology of science and feminist criticism". He was explicit about "the humanistic origins of the ‘invisible ideal in post-modernist thought'", referencing as well the ironically dystopian Philip K. Dick novel Ubik.
Dr. Ken Sakamura of the University of Tokyo, Japan leads the Ubiquitous Networking Laboratory (UNL), Tokyo as well as the T-Engine Forum. The joint goal of Sakamura's Ubiquitous Networking specification and the T-Engine forum, is to enable any everyday device to broadcast and receive information.
MIT has also contributed significant research in this field, notably Things That Think consortium (directed by Hiroshi Ishii, Joseph A. Paradiso and Rosalind Picard) at the Media Lab and the CSAIL effort known as Project Oxygen. Other major contributors include University of Washington's Ubicomp Lab (directed by Shwetak Patel), Georgia Tech's College of Computing, Cornell University's People Aware Computing Lab, NYU's Interactive Telecommunications Program, UC Irvine's Department of Informatics, Microsoft Research, Intel Research and Equator, Ajou University UCRi & CUS.
One of the earliest ubiquitous systems was artist Natalie Jeremijenko's "Live Wire", also known as "Dangling String", installed at Xerox PARC during Mark Weiser's time there. This was a piece of string attached to a stepper motor and controlled by a LAN connection; network activity caused the string to twitch, yielding a peripherally noticeable indication of traffic. Weiser called this an example of calm technology.
Ambient Devices has produced an "orb", a "dashboard", and a "weather beacon": these decorative devices receive data from a wireless network and report current events, such as stock prices and the weather, like the Nabaztag produced by Violet Snowden.
The Unified Computer Intelligence Corporation has launched a device called Ubi - The Ubiquitous Computer that is designed to allow voice interaction with the home and provide constant access to information.
Current research 
See also 
- Augmented reality
- Ambient intelligence
- Context-aware pervasive systems
- Human-centered computing
- Human-computer interaction
- Physical computing
- Real Virtuality
- Sensor grid
- Sentient computing
- Smart device
- Task computing
- Ubiquitous learning
- Ubiquitous Commerce
- Virtual reality
- Wearable computer
- J. York, P.C. Pendharkar, "Human–computer interaction issues for mobile computing in a variable work context", Int. J. Human-Computer Studies 60 (2004) 771–797
- Hansmann, Uwe (2003). Pervasive Computing: The Mobile World. Springer. ISBN 3-540-00218-9.
- Greenfield, Adam (2006). Everyware: the dawning age of ubiquitous computing. New Riders. pp. 11–12. ISBN 0-321-38401-6.
- "World Haptics Conferences". Haptics Technical Committee. Retrieved 2007-10-13.
- Poslad, Stefan (2009). Ubiquitous Computing Smart Devices, Smart Environments and Smart Interaction. Wiley. ISBN 978-0-470-03560-3.
- Weiser, Mark (1991). "The Computer for the 21st Century". Retrieved 2012-12-19.
- Weiser; Gold; Brown (1999-05-11). "Ubiquitous computing". Retrieved 2008-05-07.
- Weiser, Mark (1996-03-17). "Ubiquitous computing". Retrieved 2007-11-03.
- ieeexplore.ieee.org; T-Engine, arguably the most advanced ubiquitous computing platform in the world
- "MIT Media Lab - Things That Think Consortium". MIT. Retrieved 2007-11-03.
- "MIT Project Oxygen: Overview". MIT. Retrieved 2007-11-03.
- "Equator". UCL. Retrieved 2009-11-19.
- "Center_of_excellence_for_Ubiquitous_System". CUS. Retrieved 2008-05-04.
- Weiser, Mark; Rich Gold and John Seely Brown (1999). "The origins of ubiquitous computing research at PARC in the late 1980s". IBM systems journal 38 (4): 693. doi:10.1147/sj.384.0693.
An introduction to the field appropriate for general audiences is Adam Greenfield's book Everyware: The Dawning Age of Ubiquitous Computing (ISBN 0-321-38401-6). Greenfield describes the interaction paradigm of ubiquitous computing as "information processing dissolving in behavior".
Conferences in the field include:
- International Conference on Pervasive Computing (Pervasive)
- ACM International Conference on Ubiquitous Computing (Ubicomp)
- IEEE International Conference on Pervasive Computing and Communications (Percom)
- IEEE International Conference on Pervasive Services (ICPS)
- IEEE GlobeCom Workshop on Service Discovery and Composition in Ubiquitous and Pervasive Environments (SUPE)
- The Second International Conference on Mobile Ubiquitous Computing, Systems, Services and Technologies (UBICOMM 2008)
Academic journals and magazines devoted primarily to pervasive computing:
- Pervasive Computing (IEEE)
- Personal and Ubiquitous Computing (Springer)
- Pervasive and Mobile Computing journal, PMC (Elsevier)
- Ubiquitous Computing and Communication Journal - UbiCC Journal
Mark Weiser's original material dating from his tenure at Xerox PARC:
- Context and Adaptivity in Pervasive Computing Environments: Links with Software Engineering and Ontological Engineering, article in Journal of Software, Vol 4, No 9 (2009), 992-1013, Nov 2009 by Ahmet Soylu, Patrick De Causmaecker and Piet Desmet
- Yesterday’s tomorrows: notes on ubiquitous computing’s dominant vision, by Genevieve Bell & Paul Dourish.
- Towards pervasive computing in health care – A literature review, article in BMC Medical Informatics and Decision Making (Open Access journal) by Carsten Orwat, Andreas Graefe and Timm Faulwasser.
- Pervasive Technology Lab (CIC) Pervasive Technology to Help People with Mental Health Problems.