Ubiquitous computing is a term used to describe the growing ability for devices and objects to be able to communicate with each other over protocols embedded in everyday objects. Ubiquitous technologies compress the space and time needed to connect to information sources. Wireless, Internet-enabled devices allow ubiquitous connectivity to an omnipresent net of data, from which we can call up any piece of data we desire. This system is both decentralized and centralized, in that we can get data from the centralized location of our handheld device, but we ourselves are decentralized in relation to the actual location of the data. This leads us to a unique moment in human history – that many of us now have the ability to be omniscient and omnipresent at the touch of a button. The omnipresent information net can send data to us from almost anywhere.
In the 1980’s, researchers at Xerox Parc talked about “the inevitable withdrawal of the computer from the desktop and into a host of old and new devices, including coffeepots, watches, microwave ovens, and copying machines. These researchers saw the computer as growing in power while withdrawing as a presence”.
The term ubiquitous computing was coined by PARC Researcher Mark Weiser 1988 to describe a future in which PCs would be replaced with invisible computers embedded in everyday objects. Weiser often referred to as the father of Ubiquitous Computing, and is known for several popular articles on early computing such as Open HouseThe Invisible Interface: Increasing the Power of the Environment through Calm Technology, Designing Calm Technology, and The Computer for the Twenty-First Century.
Ubiquitous Computing and Information
Information has become an extension of our brains into a connected, dynamic 4th dimensional field that can only be seen when we ask for a part of it. The entirety of it cannot be felt or accessed at one time, and our interfaces are still limited in the fact that we can only access this data via flat, two-dimensional screens. Belinda Barnet writes about this experience in Infomobility and Technics. "As my feet slide upon thousand-year old stone," she writes, "I am at once traveling through networks and central servers back in Australia, my details handed on via invisible network handshakes across the globe, my trajectory recorded. I am not lost, I am identifiable; I am a string of information events...I have become a roaming subscription number".
Wireless, Internet-enabled devices allow ubiquitous connectivity to an omnipresent net of data, from which we can call up any piece of data we desire. No longer do we need to seek out the nearest phone booth or wait for a specific feature to play in a movie theater – we can use mobile devices to play a clip, or use communication features to connect anywhere, at any time, in a variety of ways (both textual and auditory). Technosocial devices compress the space and time needed to connect to information sources. Our ears can reach to the next neighborhood or Japan at the mere touch of a button.
Sentient computing is a form of ubiquitous computing which uses sensors to perceive its environment and react accordingly. A common use of the sensors is to construct a world model which allows location-aware or context-aware applications to be constructed. Sentient computers use information gathered from ambient sources which sometimes entail processes that occur in the background, data that is pushed to the user, user's location, time of day, current speed, average speed over time, prior actions such as clicks and subscriptions, and user's friends on another platform.
Early Sentient Computing
One research prototype of a sentient computing system was the work at AT&T Laboratories, Cambridge. It consisted of an ultrasonic indoor location system called the "Active Bats" which provided a location accuracy of about 3 cm. The world model was managed via the SPIRIT database, using CORBA to access information and spatial indexing to deliver high-level events such as "Alice has entered the kitchen" to listening context-aware applications. Some example applications of the system included a "follow-me phone" which would cause the telephone nearest the recipient to ring, teleporting desktops via VNC just by clicking their Active Bat near the computer, spatial buttons which were activated by clicking the Active Bat at a particular spot (such as a poster), measuring and surveying buildings, and location-based games. 
- Mosco, Vincent. The Digital Sublime: Myth, Power, and Cyberspace. The MIT Press Cambridge, Massachusetts London, England. Pg 21.
- Open House (Word Doc Link) from the online journal ITP Review http://www.ubiq.com/hypertext/weiser/wholehouse.doc
- Weiser, Mark. The Invisible Interface: Increasing the Power of the Environment through Calm Technology, keynote speech at CoBuild98. http://www.springerlink.com/content/n5513146535g2n14/
- Weiser, Mark. Designing Calm Technology, coauthored with John Seely Brown. http://www.ubiq.com/hypertext/weiser/calmtech/calmtech.htm
- Weiser, Mark. The Computer for the Twenty-First Century. Scientific American, 1991. http://www.ubiq.com/hypertext/weiser/SciAmDraft3.html
- Barnet, Belinda. Infomobility and Technics: some travel notes. 1000 Days of Theory. Published Oct. 27, 2005. Accessed April 2011. http://www.ctheory.net/articles.aspx?id=492
- The Bat System 3D Ultrasonic Positioning for People and Objects. DTG Research. Cambridge University. Accessed Oct 2011. http://www.cl.cam.ac.uk/research/dtg/research/wiki/BatSystem
- Sentient Computing http://en.wikipedia.org/wiki/Sentient_computing