10-08-2013, 04:07 PM
Pervasive Computing: A Paradigm for the 21st Century
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INTRODUCTION
In 1991, Mark Weiser, then chief technology officer for Xerox’s Palo
Alto Research Center, described a vision for 21st century computing
that countered the ubiquity of personal computers. “The most pro-
found technologies are those that disappear,” he wrote. “They weave
themselves into the fabric of everyday life until they are indistin-
guishable from it.”1
Computing has since mobilized itself beyond the desktop PC. Significant
hardware developments—as well as advances in location sensors, wireless
communications, and global networking—have advanced Weiser’s vision
toward technical and economic viability. Moreover, the Web has diffused
some of the psychological barriers that he also thought would have to dis-
appear.
However, the integration of information technology into our lives still
falls short of Weiser’s concluding vision:
There is more information available at our fingertips during a walk in the
woods than in any computer system, yet people find a walk among trees relax-
ing and computers frustrating. Machines that fit the human environment
instead of forcing humans to enter theirs will make using a computer as refresh-
ing as taking a walk in the woods.
EVOLUTION OF PERVASIVE COMPUTING
Pervasive computing defines a major evolution-
ary step in work that began in the mid 1970s, when
the PC first brought computers closer to people. In
Weiser’s vision, however, the idea of making a com-
puter personal is technologically misplaced. In fact,
it keeps computing separate from our daily life.
Although the PC has not delivered the full poten-
tial of information technology to users, it certainly
took a first step toward making computers (if not
computing) popular (if not pervasive). It was also
an instrumental factor in the phenomenal growth
of hardware components and the development of
graphical user interfaces.
Distributed computing
With the advent of networking, personal com-
puting evolved to distributed computing. As com-
puters became connected, they began to share
capabilities over the network. Distributed com-
puting marked the next step toward pervasive com-
puting by introducing seamless access to remote
information resources and communication with
fault tolerance, high availability, and security.3
Although the World Wide Web was not designed
to be a distributed computing infrastructure, its net-
working ubiquity has made it an attractive choice
for experimenting with distributed computing con-
cepts. It has also created a culture that is substan-
tially more amenable to the deployment of
pervasive computing environments than the culture
that existed when Weiser first articulated his vision.
The ad hoc nature of the Web’s growth has proved
that we can distribute computing capabilities in a
big way without losing scalability. The simple
mechanisms for linking resources have provided a
means for integrating distributed information bases
into a single structure.
Pervasive middleware
Like distributed computing and mobile comput-
ing, pervasive computing requires a middleware
“shell” to interface between the networking kernel
and the end-user applications running on pervasive
devices. As Figure 2 shows, this pervasive middle-
ware will mediate interactions with the network-
ing kernel on the user’s behalf and will keep users
immersed in the pervasive computing space. The
middleware will consist mostly of firmware and
software bundles executing in either client-server
or peer-to-peer mode.
User interfaces are another aspect of middleware.
Standard Web browsers represent the high end of
interface sophistication. They use more color,
graphics, and controls than users typically expect
on pervasive devices. Mobile computing has
already introduced microbrowsers. For example,
phone.com’s UP.Browser is implemented on sev-
eral commercially available digital phones.
Scalability
Future pervasive computing environments will
likely face a proliferation of users, applications, net-
worked devices, and their interactions on a scale
never experienced before. As environmental smart-
ness grows, so will the number of devices connected
to the environment and the intensity of human-
machine interactions.
Traditional development requires recreating the
application for each new device. Even if an enterprise
could generate new applications as fast as it adds new
devices, writing application logic only once—inde-
pendent of devices—would have tremendous value in
solving the applications scalability problem.
Furthermore, applications typically are distrib-
uted and installed separately for each device class
and processor family. As the number of devices
grows, explicitly distributing and installing appli-
cations for each class and family will become
unmanageable, especially across a wide geographic
area.
Portolano
In its Portolano project (portolano.cs.washington.
edu/), the University of Washington seeks to create
a testbed for investigating pervasive computing.
The project emphasizes invisible, intent-based com-
puting, which infers users’ intentions via their
actions in the environment and their interactions
with everyday objects.
Project devices are highly optimized to particu-
lar tasks so that they blend into the world and
require little technical knowledge on the user’s part.
In short, Portolano proposes an infrastructure
based on mobile agents that interact with applica-
tions and users. Data-centric routing automatically
migrates data among applications on the user’s
behalf. Data thus becomes “smart,” and serves as
an interaction mechanism within the environment.
Sentient Computing
AT&T Laboratories, Cambridge, UK, is collab-
orating with the Cambridge University Engineering
Department on the Sentient Computing project
(www.uk.research.attspirit/). The project
explores user interfaces that employ sensors and
resource status data to maintain a world model
shared by users and applications.
The world model for the Sentient Computing
project covers an entire building. Interfaces to pro-
grams extend seamlessly throughout the building.
Computer desktops follow their owners and reflect
real-time updates for object locations. This project
has led to some new kinds of applications, like con-
text-aware filing systems and smart posters.