mark weiser (1952–1999) - lyle school of...

18 PERVASIVEcomputing

Mark Weiserwas the chief technology officer at Xerox’s Palo Alto Research Cen-ter (Parc). He is often referred to as the father of ubiquitous computing. He coined theterm in 1988 to describe a future in which invisible computers, embedded in everydayobjects, replace PCs. Other research interests included garbage collection, operating sys-tems, and user interface design. He received his MA and PhD in computer and com-munication science at the University of Michigan, Ann Arbor. After completing his PhD,he joined the computer science department at the University of Maryland, College Park,where he taught for 12 years. He wrote or cowrote over 75 technical publications on suchsubjects as the psychology of programming, program slicing, operating systems, pro-gramming environments, garbage collection, and technological ethics. He was a mem-ber of the ACM, IEEE Computer Society, and American Association for the Advance-ment of Science. Weiser passed away in 1999. Visit www.parc.xerox.com/csl/members/weiser or contact [email protected] for more informationabout him.

Mark Weiser(1952–1999) The Founder of

Ubiquitous Computing

Mark Weiser(1952–1999) The Founder of

Ubiquitous Computing

PERVASIVEcomputing 19

The Computer for the 21st Century

T he most profound technologies arethose that disappear. They weavethemselves into the fabric of everydaylife until they are indistinguishablefrom it.

Consider writing, perhaps the first informationtechnology. The ability to represent spoken languagesymbolically for long-term storage freed informa-tion from the limits of individual memory. Todaythis technology is ubiquitous in industrialized coun-tries. Not only do books, magazines and newspa-pers convey written information, but so do streetsigns, billboards, shop signs and even graffiti. Candy

wrappers are covered in writing.The constant background pres-ence of these products of “liter-acy technology” does not requireactive attention, but the infor-

mation to be transmitted is ready for use at a glance.It is difficult to imagine modern life otherwise.

Silicon-based information technology, in contrast,is far from having become part of the environment.More than 50 million personal computers have beensold, and the computer nonetheless remains largelyin a world of its own. It is approachable onlythrough complex jargon that has nothing to do withthe tasks for which people use computers. The stateof the art is perhaps analogous to the period whenscribes had to know as much about making ink orbaking clay as they did about writing.

The arcane aura that surrounds personal com-puters is not just a “user interface” problem. My

colleagues and I at the Xerox Palo Alto ResearchCenter think that the idea of a “personal” computeritself is misplaced and that the vision of laptopmachines, dynabooks and “knowledge navigators”is only a transitional step toward achieving the realpotential of information technology. Such machinescannot truly make computing an integral, invisiblepart of people’s lives. We are therefore trying to con-ceive a new way of thinking about computers, onethat takes into account the human world and allowsthe computers themselves to vanish into the back-ground.

Such a disappearance is a fundamental conse-quence not of technology but of human psychology.Whenever people learn something sufficiently well,they cease to be aware of it. When you look at astreet sign, for example, you absorb its informationwithout consciously performing the act of reading.Computer scientist, economist and Nobelist Her-bert A. Simon calls this phenomenon “compiling”;philosopher Michael Polanyi calls it the “tacitdimension”; psychologist J.J. Gibson calls it “visualinvariants”; philosophers Hans Georg Gadamer andMartin Heidegger call it the “horizon” and the“ready-to-hand”; John Seely Brown of PARC callsit the “periphery.” All say, in essence, that only whenthings disappear in this way are we freed to use themwithout thinking and so to focus beyond them onnew goals.

The idea of integrating computers seamlessly intothe world at large runs counter to a number of pre-

Specialized elements of hardware and software, connected by wires,radio waves and infrared, will be so ubiquitous that no one will noticetheir presence.

R E A C H I N G F O R W E I S E R ’ S V I S I O N

By Mark Weiser

Reprinted with permission. Copyright 1991 by Scientific American, Inc. All rights reserved.

Images not reprinted. Some were omitted and others reproduced.

sent-day trends. “Ubiquitous computing”in this context does not mean just com-puters that can be carried to the beach, jun-gle or airport. Even the most powerfulnotebook computer, with access to aworldwide information network, stillfocuses attention on a single box. By anal-ogy with writing, carrying a superlaptop islike owning just one very important book.Customizing this book, even writing mil-lions of other books, does not begin to cap-ture the real power of literacy.

Furthermore, although ubiquitous com-puters may use sound and video in additionto text and graphics, that does not makethem “multimedia computers.” Today’smultimedia machine makes the computerscreen into a demanding focus of attentionrather than allowing it to fade into thebackground.

Perhaps most diametrically opposed toour vision is the notion of virtual reality,which attempts to make a world inside thecomputer. Users don special goggles thatproject an artificial scene onto their eyes;they wear gloves or even bodysuits thatsense their motions and gestures so thatthey can move about and manipulate vir-tual objects. Although it may have its pur-pose in allowing people to explore realms

otherwise inaccessible—the insides of cells,the surfaces of distant planets, the infor-mation web of data bases—virtual realityis only a map, not a territory. It excludesdesks, offices, other people not wearinggoggles and bodysuits, weather, trees,walks, chance encounters and, in general,the infinite richness of the universe. Virtualreality focuses an enormous apparatus onsimulating the world rather than on invis-ibly enhancing the world that already exists.

Indeed, the opposition between thenotion of virtual reality and ubiquitous,invisible computing is so strong that someof us use the term “embodied virtuality” torefer to the process of drawing computersout of their electronic shells. The “virtual-ity” of computer-readable data—all the dif-ferent ways in which they can be altered,processed and analyzed—is brought intothe physical world.

How do technologies disappear into thebackground? The vanishing of electricmotors may serve as an instructive exam-ple. At the turn of the century, a typicalworkshop or factory contained a singleengine that drove dozens or hundreds ofdifferent machines through a system ofshafts and pulleys. Cheap, small, efficient

electric motors made it possible first to giveeach tool its own source of motive force,then to put many motors into a singlemachine.

A glance through the shop manual of atypical automobile, for example, reveals 22motors and 25 solenoids. They start theengine, clean the windshield, lock andunlock the doors, and so on. By payingcareful attention, the driver might be able todiscern whenever he or she activated amotor, but there would be no point to it.

Most computers that participate inembodied virtuality will be invisible in factas well as in metaphor. Already computersin light switches, thermostats, stereos andovens help to activate the world. Thesemachines and more will be interconnectedin a ubiquitous network. As computer sci-entists, however, my colleagues and I havefocused on devices that transmit and dis-play information more directly. We havefound two issues of crucial importance:location and scale. Little is more basic tohuman perception than physical juxtapo-sition, and so ubiquitous computers mustknow where they are. (Today’s computers,in contrast, have no idea of their locationand surroundings.) If a computer knowsmerely what room it is in, it can adapt itsbehavior in significant ways without requir-ing even a hint of artificial intelligence.

Ubiquitous computers will also come indifferent sizes, each suited to a particulartask. My colleagues and I have built whatwe call tabs, pads and boards: inch-scalemachines that approximate active Post-itnotes, foot-scale ones that behave some-thing like a sheet of paper (or a book or a

20 PERVASIVEcomputing http://computer.org/pervasive


Tab

Workstation File server Laser printer

Pad

InfraredRadio

frequencyInfrared

Radiofrequency

WIRED AND WIRELESS NETWORKS linkcomputers and allow their users to shareprograms and data. The computerspictured here include conventionalterminals and file servers, pocket-sizemachines known as tabs and page-sizeones known as pads. Future networksmust be capable of supporting hundredsof devices in a single room and must alsocope with devices—ranging from tabs tolaser printers or large-screen displays—that move from one place to another.

magazine) and yard-scale displays that arethe equivalent of a blackboard or bulletinboard.

How many tabs, pads and board-sizewriting and display surfaces are there in atypical room? Look around you: at theinch scale, include wall notes, titles onbook spines, labels on controls, ther-mostats and clocks, as well as small piecesof paper. Depending on the room, you maysee more than 100 tabs, 10 or 20 pads andone or two boards. This leads to our goalfor initially deploying the hardware ofembodied virtuality: hundreds of comput-ers per room.

Hundreds of computers in a room couldseem intimidating at first, just as hundredsof volts coursing through wires in the wallsonce did. But like the wires in the walls,these hundreds of computers will come tobe invisible to common awareness. Peoplewill simply use them unconsciously toaccomplish everyday tasks.

Tabs are the smallest components ofembodied virtuality. Because they are inter-connected, tabs will expand on the useful-ness of existing inch-scale computers, suchas the pocket calculator and the pocketorganizer. Tabs will also take on functionsthat no computer performs today. Forexample, computer scientists at PARC andother research laboratories around theworld have begun working with activebadges—clip-on computers roughly the

size of an employee I.D. card, first devel-oped by the Olivetti Cambridge researchlaboratory. These badges can identifythemselves to receivers placed throughouta building, thus making it possible to keeptrack of the people or objects to which theyare attached.

In our experimental embodied virtuality,doors open only to the right badge wearer,rooms greet people by name, telephone callscan be automatically forwarded to wher-ever the recipient may be, receptionistsactually know where people are, computerterminals retrieve the preferences of who-ever is sitting at them, and appointmentdiaries write themselves. The automaticdiary shows how such a simple task asknowing where people are can yield com-plex dividends: meetings, for example, con-sist of several people spending time in thesame room, and the subject of a meeting ismost probably the files called up on thatroom’s display screen while the people arethere. No revolution in artificial intelligenceis needed, merely computers embedded inthe everyday world.

My colleague Roy Want has designed atab incorporating a small display that canserve simultaneously as an active badge, cal-endar and diary. It will also act as an exten-sion to computer screens: instead of shrink-ing a program window down to a small iconon the screen, for example, a user will be ableto shrink the window onto a tab display. This

will leave the screen free for information andalso let people arrange their computer-basedprojects in the area around their terminals,much as they now arrange paper-based pro-jects in piles on desks and tables. Carrying aproject to a different office for discussion isas simple as gathering up its tabs; the asso-ciated programs and files can be called upon any terminal.

The next step up in size is the pad, some-thing of a cross between a sheet of paperand current laptop and palmtop computers.Robert Krivacic of PARC has built a proto-type pad that uses two microprocessors, aworkstation-size display, a multibutton sty-lus and a radio network with enough com-munications bandwidth to support hun-dreds of devices per person per room.

Pads differ from conventional portablecomputers in one crucial way. Whereasportable computers go everywhere withtheir owners, the pad that must be carriedfrom place to place is a failure. Pads areintended to be “scrap computers” (analo-gous to scrap paper) that can be grabbedand used anywhere; they have no individ-ualized identity or importance.

One way to think of pads is as an anti-dote to windows. Windows were inventedat PARC and popularized by Apple in theMacintosh as a way of fitting several dif-ferent activities onto the small space of acomputer screen at the same time. In 20

JANUARY–MARCH 2002 PERVASIVEcomputing 21

Control button

Batteries

Infrared light-emitting diodes

Microprocessor

Chris KentXerox PARC

The Active Badge. This harbinger of inch-scale computers contains a small microprocessor and an infrared transmitter. The badgebroadcasts the identity of its wearer and so can trigger automatic doors, automatic telephone forwarding and computer displayscustomized to each person reading them. The active badge and other networked tiny computers are called tabs.

years computer screens have not grownmuch larger. Computer window systemsare often said to be based on the desktopmetaphor—but who would ever use a deskonly nine inches high by 11 inches wide?

Pads, in contrast, use a real desk. Spreadmany electronic pads around on the desk,just as you spread out papers. Have manytasks in front of you, and use the pads asreminders. Go beyond the desk to draw-ers, shelves, coffee tables. Spread the manyparts of the many tasks of the day out infront of you to fit both the task and thereach of your arms and eyes rather than tofit the limitations of glassblowing. Some-day pads may even be as small and light asactual paper, but meanwhile they can ful-fill many more of paper’s functions thancan computer screens.

Yard-size displays (boards) serve a num-ber of purposes: in the home, video screensand bulletin boards; in the office, bulletinboards, white boards or flip charts. Aboard might also serve as an electronicbookcase from which one might download

texts to a pad or tab. For the time being,however, the ability to pull out a book andplace it comfortably on one’s lap remainsone of the many attractions of paper. Sim-ilar objections apply to using a board as adesktop; people will have to become accus-tomed to having pads and tabs on a deskas an adjunct to computer screens beforetaking embodied virtuality any further.

Prototype boards, built by Richard Bruceand Scott Elrod of PARC, are in use at sev-eral Xerox research laboratories. They mea-sure about 40 by 60 inches and display1,024 ! 768 black-and-white pixels. Tomanipulate the display, users pick up a pieceof wireless electronic “chalk” that can workeither in contact with the surface or from adistance. Some researchers, using them-selves and their colleagues as guinea pigs,

can hold electronically mediated meetingsor engage in other forms of collaborationaround a live board. Others use the boardsas testbeds for improved display hardware,new “chalk” and interactive software.

For both obvious and subtle reasons, thesoftware that animates a large shared dis-play and its electronic chalk is not the sameas that for a workstation. Switching backand forth between chalk and keyboardmay involve walking several steps, and sothe act is qualitatively different from usinga keyboard and mouse. In addition, bodysize is an issue. Not everyone can reach thetop of the board, so a Macintosh-stylemenu bar might have to run across the bot-tom of the screen instead.

We have built enough live boards to per-mit casual use: they have been placed inordinary conference rooms and open areas,and no one need sign up or give advancenotice before using them. By building andusing these boards, researchers start toexperience and so understand a world inwhich computer interaction informally

enhances every room. Live boards can use-fully be shared across rooms as well aswithin them. In experiments instigated byPaul Dourish of EuroPARC and Sara Blyand Frank Halasz of PARC, groups atwidely separated sites gathered aroundboards—each displaying the same image—and jointly composed pictures and draw-ings. They have even shared two boardsacross the Atlantic.

Live boards can also be used as bulletinboards. There is already too much text forpeople to read and comprehend all of it,and so Marvin Theimer and David Nicholsof PARC have built a prototype system thatattunes its public information to the peo-ple reading it. Their “scoreboard” requireslittle or no interaction from the user otherthan to look and to wear an active badge.

Prototype tabs, pads and boards are justthe beginning of ubiquitous computing.The real power of the concept comes notfrom any one of these devices—it emergesfrom the interaction of all of them. Thehundreds of processors and displays arenot a “user interface” like a mouse andwindows, just a pleasant and effective“place” to get things done.

What will be most pleasant and effectiveis that tabs can animate objects previouslyinert. They can beep to help locate mislaidpapers, books or other items. File drawerscan open and show the desired folder—nosearching. Tabs in library catalogues canmake active maps to any book and guidesearchers to it, even if it is off the shelf, lefton a table by the last reader.

In presentations, the size of text on over-head slides, the volume of the amplifiedvoice, even the amount of ambient light,can be determined not by guesswork butby the desires of the listeners in the roomat that moment. Software tools for tally-ing votes instantly and consensus checkingare already available in electronic meetingrooms of some large corporations; tabs canmake them widespread.

The technology required for ubiquitouscomputing comes in three parts: cheap,low-power computers that include equallyconvenient displays, software for ubiqui-tous applications and a network that tiesthem all together. Current trends suggestthat the first of these requirements will eas-ily be met. Flat-panel displays containing640 ! 480 black-and-white pixels are nowcommon. This is the standard size for PCsand is also about right for television. Aslong as laptop, palmtop and notebookcomputers continue to grow in popularity,display prices will fall, and resolution andquality will rise. By the end of the decade,a 1,000 ! 800-pixel high-contrast displaywill be a fraction of a centimeter thick andweigh perhaps 100 grams. A small batterywill provide several days of continuous use.

Larger displays are a somewhat differ-ent issue. If an interactive computer screenis to match a white board in usefulness, itmust be viewable from arm’s length as wellas from across a room. For close viewing,



Prototype tabs, pads and boards are just the

beginning of ubiquitous computing.

The real power of the concept emerges from

the interaction of all of them.

the density of picture elements should beno worse than on a standard computerscreen, about 80 per inch. Maintaining adensity of 80 pixels per inch over an areaseveral feet on a side implies displaying tensof millions of pixels. The biggest computerscreen made today has only about onefourth that capacity. Such large displayswill probably be expensive, but they shouldcertainly be available.

The large display will require advancedmicroprocessors to feed it. Central-pro-cessing-unit speeds reached a millioninstructions per second in 1986 and con-tinue to double each year. Some industryobservers believe that this exponentialgrowth in raw chip speed may begin tolevel off about 1994 but that other mea-sures of performance, including powerconsumption and auxiliary functions, willstill improve. The 100-gram flat-panel dis-play, then, might be driven by a micro-processor that executes a billion operationsper second and contains 16 megabytes ofon-board memory along with sound, videoand network interfaces. Such a processorwould draw, on average, a few percent ofthe power required by the display.

Auxiliary storage devices will augmentmain memory capacity: conservativeextrapolation of current technology sug-gests that removable hard disks (or non-volatile memory chips) the size of a match-book will store about 60 megabytes each.Larger disks containing several gigabytesof information will be standard, and ter-abyte storage—roughly the data contentof the Library of Congress—will be com-mon. Such enormous stores will not nec-

essarily be filled to capacity with usableinformation. Abundant space will, how-ever, allow radically different strategies ofinformation management. A terabyte ofdisk storage will make deleting old files vir-tually unnecessary, for example.

Although processors and displaysshould be capable of offering ubiquitouscomputing by the end of the decade, trendsin software and network technology aremore problematic. Current implementa-tions of “distributed computing” simplymake networked file servers, printers orother devices appear as if they were con-nected directly to each user’s computer.This approach, however, does nothing toexploit the unique capabilities of physicallydispersed computers and the informationembodied in knowing where a particulardevice is located.

Computer operating systems and win-dow-based display software will have tochange substantially. The design of currentoperating systems, such as DOS and Unix,is based on the assumption that a com-puter’s hardware and software configura-tion will not change substantially while itis running. This assumption is reasonablefor conventional mainframes and personalcomputers, but it makes no sense in termsof ubiquitous computing. Pads, tabs andeven boards may come and go at any timein any room, and it will certainly be impos-sible to shut down all the computers in aroom to install new software in any one ofthem. (Indeed, it may be impossible to findall the computers in a room.)

One solution may be “micro-kernel”

operating systems such as those developedby Rick Rashid of Carnegie Mellon Uni-versity and A.S. Tanenbaum of Vrije Uni-versity in Amsterdam. These experimentalsystems contain only the barest scaffoldingof fixed computer code; software modulesto perform specific functions can be read-ily added or removed. Future operating sys-tems based on this principle could shrinkand grow automatically to fit the changingneeds of ubiquitous computation.

Current window display systems alsoare not ready to cope with ubiquitous com-puting. They typically assume that a par-ticular computer will display all the infor-mation for a single application. Althoughthe X Window System and Windows 3.0,for example, can cope with multiplescreens, they do not do well with applica-tions that start out on one screen and moveto another, much less those that peregri-nate from computer to computer or roomto room.

Solutions to this problem are in theirinfancy. Certainly no existing display sys-tem can perform well while working withthe full diversity of input and output formsrequired by embodied virtuality. Makingpads, tabs and boards work together seam-lessly will require changes in the kinds ofprotocols by which applications programsand their displayed windows communicate.

The network that will connect ubiqui-tous hardware and software poses furtherchallenges. Data transmission rates for bothwired and wireless networks are increasingrapidly. Access to gigabit-per-second wirednets is already possible, although expen-sive, and will become progressively cheaper.


THE TACIT DIMENSION. Michael Polanyi. Doubleday & Company,1966.

TOWARD PORTABLE IDEAS. Mark Stefik and John Seely Brown in Tech-nological Support for Work Group Collaboration. Edited by Mar-grethe H. Olson. Lawrence Erlbaum Associates, 1989.

RECENT DEVELOPMENTS IN OPERATING SYSTEMS. Special issue of Com-puter (IEEE Computer Society), Vol. 23, No. 5; May 1990.

ACTIVITY BASED INFORMATION RETRIEVAL: TECHNOLOGY IN SUPPORT OF

HUMAN MEMORY. Mik Lamming and William Newman. Available asRank Xerox EuroPARC Technical Report 91-03; February 1991 .

LCDS AND BEYOND. Nick Baran in Byte, Vol. 16, No. 2, pages229–236; February 1991.

A TALK WITH INTEL. Kenneth M. Sheldon in Byte, Vol. 16, No. 4,pages 131–140; April 1991.

Further Reading

(Gigabit networks will seldom devote all oftheir bandwidth to a single data stream;instead they will allow enormous numbersof lower-speed transmissions to proceedsimultaneously.) Small wireless networks,based on digital cellular telephone princi-ples, currently offer data rates between twoand 10 megabits per second over a rangeof a few hundred meters. Low-power wire-less networks capable of transmitting250,000 bits per second to each station willeventually be available commercially.

Yet the problem of transparently linkingwired and wireless networks resists solu-tion. Although some stopgap methods havebeen developed, engineers must developnew communications protocols that explic-itly recognize the concept of machines thatmove in physical space. Furthermore, thenumber of channels envisioned in mostwireless network schemes is still very small,and the range large (50 to 100 meters), sothat the total number of mobile devices isseverely limited. The ability of such a sys-

tem to support hundreds of machines inevery room is out of the question. Single-room networks based on infrared or newerelectromagnetic technologies have enoughchannel capacity for ubiquitous computers,but they can work only indoors.

Present technologies would require amobile device to have three different net-work connections: tiny-range wireless,long-range wireless and very high speedwired. A single kind of network connec-tion that can somehow serve all three func-tions has yet to be invented.

Neither an explication of the principlesof ubiquitous computing nor a list of thetechnologies involved really gives a senseof what it would be like to live in a worldfull of invisible widgets. Extrapolating fromtoday’s rudimentary fragments of embod-

ied virtuality is like trying to predict thepublication of Finnegans Wake shortly afterhaving inscribed the first clay tablets. Nev-ertheless, the effort is probably worthwhile:

Sal awakens; she smells coffee. A fewminutes ago her alarm clock, alerted by herrestless rolling before waking, had quietlyasked, “Coffee?” and she had mumbled,“Yes.” “Yes” and “no” are the only wordsit knows.

Sal looks out her windows at her neigh-borhood. Sunlight and a fence are visiblethrough one, and through others she seeselectronic trails that have been kept for herof neighbors coming and going during theearly morning. Privacy conventions andpractical data rates prevent displayingvideo footage, but time markers and elec-tronic tracks on the neighborhood map letSal feel cozy in her street.

Glancing at the windows to her kids’rooms, she can see that they got up 15 and20 minutes ago and are already in the

kitchen. Noticing that she is up, they startmaking more noise.

At breakfast Sal reads the news. She stillprefers the paper form, as do most people.She spots an interesting quote from a colum-nist in the business section. She wipes herpen over the newspaper’s name, date, sec-tion and page number and then circles thequote. The pen sends a message to the paper,which transmits the quote to her office.

Electronic mail arrives from the companythat made her garage door opener. She hadlost the instruction manual and asked themfor help. They have sent her a new manualand also something unexpected—a way tofind the old one. According to the note, shecan press a code into the opener and themissing manual will find itself. In the garage,she tracks a beeping noise to where the oil-stained manual had fallen behind some

boxes. Sure enough, there is the tiny tab themanufacturer had affixed in the cover to tryto avoid Email requests like her own.

On the way to work Sal glances in the fore-view mirror to check the traffic. She spots aslowdown ahead and also notices on a sidestreet the telltale green in the foreview of afood shop, and a new one at that. She decidesto take the next exit and get a cup of coffeewhile avoiding the jam.

Once Sal arrives at work, the foreviewhelps her find a parking spot quickly. Asshe walks into the building, the machinesin her office prepare to log her in but donot complete the sequence until she actu-ally enters her office. On her way, she stopsby the offices of four or five colleagues toexchange greetings and news.

Sal glances out her windows: a gray dayin Silicon Valley, 75 percent humidity and40 percent chance of afternoon showers;meanwhile it has been a quiet morning atthe East Coast office. Usually the activityindicator shows at least one spontaneous,urgent meeting by now. She chooses not toshift the window on the home office backthree hours—too much chance of beingcaught by surprise. But she knows otherswho do, usually people who never get a callfrom the East but just want to feel involved.

The telltale by the door that Sal pro-grammed her first day on the job is blink-ing: fresh coffee. She heads for the coffeemachine.

Coming back to her office, Sal picks upa tab and “waves” it to her friend Joe in thedesign group, with whom she has a jointassignment. They are sharing a virtual officefor a few weeks. The sharing can take manyforms—in this case, the two have giveneach other access to their location detectorsand to each other’s screen contents andlocation. Sal chooses to keep miniature ver-sions of all Joe’s tabs and pads in view andthree-dimensionally correct in a little suiteof tabs in the back corner of her desk. Shecan’t see what anything says, but she feelsmore in touch with his work when notic-ing the displays change out of the corner ofher eye, and she can easily enlarge anythingif necessary.

A blank tab on Sal’s desk beeps and dis-plays the word “Joe” on it. She picks it up



Neither an explication of the principles of

ubiquitous computing nor a list of the technologies

involved really gives a sense of what it would be

like to live in a world full of invisible widgets.

and gestures with it toward her live board.Joe wants to discuss a document with her,and now it shows up on the wall as shehears Joe’s voice:

“I’ve been wrestling with this third para-graph all morning, and it still has thewrong tone. Would you mind reading it?”

Sitting back and reading the paragraph,Sal wants to point to a word. She gesturesagain with the “Joe” tab onto a nearby padand then uses the stylus to circle the wordshe wants:

“I think it’s this term ‘ubiquitous.’ It’s justnot in common enough use and makes thewhole passage sound a little formal. Canwe rephrase the sentence to get rid of it?”

“I’ll try that. Say, by the way, Sal, didyou ever hear from Mary Hausdorf?”

“No. Who’s that?” “You remember. She was at the meeting

last week. She told me she was going to getin touch with you.”

Sal doesn’t remember Mary, but she doesvaguely remember the meeting. She quicklystarts a search for meetings held during thepast two weeks with more than six peoplenot previously in meetings with her andfinds the one. The attendees’ names popup, and she sees Mary.

As is common in meetings, Mary madesome biographical information about her-self available to the other attendees, andSal sees some common background. She’lljust send Mary a note and see what’s up.Sal is glad Mary did not make the biogra-phy available only during the time of themeeting, as many people do....

In addition to showing some of the waysthat computers can enter invisibly into peo-ple’s lives, this scenario points up some ofthe social issues that embodied virtualitywill engender. Perhaps key among them isprivacy: hundreds of computers in everyroom, all capable of sensing people nearthem and linked by high-speed networks,have the potential to make totalitarianismup to now seem like sheerest anarchy. Justas a workstation on a local area networkcan be programmed to intercept messagesmeant for others, a single rogue tab in aroom could potentially record everythingthat happened there.

Even today the active badges and self-writing appointment diaries that offer allkinds of convenience could be a source ofreal harm in the wrong hands. Not onlycorporate superiors or underlings but alsooverzealous government officials and evenmarketing firms could make unpleasantuse of the same information that makesinvisible computers so convenient.

Fortunately, cryptographic techniquesalready exist to secure messages from oneubiquitous computer to another and tosafeguard private information stored in

networked systems. If designed into sys-tems from the outset, these techniques canensure that private data do not becomepublic. A well-implemented version ofubiquitous computing could even affordbetter privacy protection than exists today.

By pushing computers into the back-ground, embodied virtuality will makeindividuals more aware of the people onthe other ends of their computer links. Thisdevelopment may reverse the unhealthycentripetal forces that conventional per-sonal computers have introduced into lifeand the workplace.

Even today, people holed up in win-dowless offices before glowing computerscreens may not see their fellows for thebetter part of each day. And in virtual real-ity, the outside world and all its inhabitantseffectively cease to exist. Ubiquitous com-puters, in contrast, reside in the humanworld and pose no barrier to personalinteractions. If anything, the transparentconnections that they offer between dif-ferent locations and times may tend tobring communities closer together.

My colleagues and I at PARC believethat what we call ubiquitous computingwill gradually emerge as the dominantmode of computer access over the next 20

years. Like the personal computer, ubiqui-tous computing will produce nothing fun-damentally new, but by making everythingfaster and easier to do, with less strain andfewer mental gymnastics, it will transformwhat is apparently possible. Desktop pub-lishing, for example, is essentially no dif-ferent from computer typesetting, whichdates back to the mid-1960s. But ease ofuse makes an enormous difference.

When almost every object either con-tains a computer or can have a tab attachedto it, obtaining information will be trivial:

“Who made that dress? Are there any morein the store? What was the name of thedesigner of that suit I liked last week?” Thecomputing environment knows the suityou looked at for a long time last weekbecause it knows both of your locations,and it can retroactively find the designer’sname even though that information did notinterest you at the time.

Sociologically, ubiquitous computing maymean the decline of the computer addict. Inthe 1910s and 1920s many people “hacked”on crystal sets to take advantage of the newhigh-tech world of radio. Now crystal-and-cat’s-whisker receivers are rare because high-quality radios are ubiquitous. In addition,embodied virtuality will bring computers tothe presidents of industries and countries fornearly the first time. Computer access willpenetrate all groups in society.

Most important, ubiquitous computerswill help overcome the problem of infor-mation overload. There is more informa-tion available at our fingertips during awalk in the woods than in any computersystem, yet people find a walk among treesrelaxing and computers frustrating.Machines that fit the human environmentinstead of forcing humans to enter theirswill make using a computer as refreshing astaking a walk in the woods.


By pushing computers into the background,

embodied virtuality will make individuals

more aware of the people on the other ends

of their computer links.

mark weiser (1952–1999) - lyle school of...

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