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14.4 Sensors and ubiquitous computing 437

14.4.1 HISTORY AND EXAMPLES
The origins of ubiquitous computing are generally traced back to Marc Weiser's 1991
article “The Computer for the 21st century” (Weiser, 1991). Writing as chief tech-
nologist of the Xerox Palo Alto Research Labs—home of pioneering work in early
graphical user interfaces—Weiser imagined a future working environment with active
badges, computational devices, and pads and tabs linked by networks of wired and
wireless transceivers. Perhaps more importantly, Weiser urged the notion of “embodied
virtuality”—taking computing from the workstations of the time and embedding it in
numerous, ubiquitous devices. Coming at a time when sensors and wireless communi-
cation were beginning to be sufficiently small, powerful, and inexpensive to enable this
computing infrastructure (Weiser, 1991). Weiser's vision inspired researchers to cre-
ate the field of Ubiquitous computing, led by the flagship UbiComp conference since
2001. A 2011 study of research and co-citation in ubiquitous computing identified al-
most 6000 papers published between 1995 and 2009 (Zhao and Wang, 2011)—a num-
ber that has undoubtedly grown steadily since (Figure 14.2). Although a full review
of these varied research areas is beyond the scope of this section, description of some
selected research efforts will identify recurrent trends and related research methods.

FIGURE 14.2
A map of keywords from titles and abstracts (triangles) and other noun phrases (circles)
found in a collection of almost 6000 ubiquitous computing research articles published
between 1995 and 2009.
From Zhao, R., Wang, J., 2011. Visualizing the research on pervasive and ubiquitous computing.
Scientometrics 86 (3), 593–612.
Alternative input devices were an early focus of ubiquitous computing research.
Noting the short comings of mouse and keyboard input, these projects explored vari-
ous physical devices, complete with associated electronics, that might be used to
control software applications. The Tangible Bits effort described several possible
mechanisms including an arm-mounted LED screen, a horizontal back-projected
computing “surface,” and physical icons—known as “phicons”—that might be used
to represent and manipulate items in the display (Ishii and Ullmer, 1997).