contributed articles
october 2009 | vol. 52 | no. 10 | communications of the acm 127
doi: 10.1145/1562764.1562796
by ViVienne Waller and robert b. Johnston
The field of ubiquiTous compuTi n g was in s p ired
by Mark Weiser’s11 vision of computing artifacts that
disappear. “They weave themselves into the fabric
of everyday life until they are indistinguishable from
it.” Although Weiser cautioned that achieving the
vision of ubiquitous computing would require a new
way of thinking about computers, that takes into
account the natural human environment, to date
no one has articulated this new way of thinking.3
Here, we address this gap, making the argument that
ubiquitous computing artifacts need to be physically
and cognitively available. We show what this means
in practice, translating our conceptual findings
into principles for design. Examples and a specific
application scenario show how ubiquitous computing
that depends on these principles is both physically and
cognitively available, seamlessly supporting living.
The term ‘ubiquitous computing’ has been used
broadly to include pervasive or context-aware
computing, anytime-anywhere computing (access to
the same information everywhere) and even mobile
computing. Work on this ‘ubiquitous computing’ has
been largely application driven, reporting on
technical developments and new ap-
plications for RF(Radio Frequency)
ID technologies, smart phones, active
sensors, and wearable computing. The
risk is that in focusing on the techni-
cal capabilities, the end result is a host
of advanced applications that bear
little resemblance to Weiser’s original
vision. This is a classic case of not see-
ing the forest for the trees.
In this article, we want to take a walk
in the forest, that is, to suggest a new
way of thinking about how computing
artifacts can assist us in living. In doing
this, we draw on German philosopher
Martin Heidegger’s analysis of the
need for equipment to be ‘available.’1
While several influential studies in hu-
man-computer interaction (HCI) have
also drawn on Heidegger and the con-
cept of availability, these studies have
focused on physical availability. While
going some way to identifying and ad-
dressing the problems that Weiser
identified with traditional computing,
they have not gone far enough. Delving
deeper into Heidegger’s analysis, we
can explain why artifacts designed us-
ing the traditional model of computing
tend to get in the way of what we want
to do. This leads us to refine the con-
cept of physical availability and identify
the need for computing artifacts to also
be cognitively available.
We will first draw on Heidegger to
explain why it is that computing ar-
tifacts designed according to the tra-
ditional model are often a hindrance
rather than a help. The traditional con-
ception of how we use computing is
based on a particular understanding of
human action, which we have referred
to elsewhere as the deliberative theory
of action.2 According to this delibera-
tive theory of action, humans reflect
on the world before acting. Tradition-
ally computing artifacts are designed
to assist us through providing a repre-
sentation of the world which we can re-
flect on before action.10 In other words,
the traditional computing artifact re-
quires us to move away from acting in
the world to ‘use’ the computer. In the
case of the desktop computer, there is
making
ubiquitous
computing
available

128 communications of the acm | october 2009 | vol. 52 | no. 10
contributed articles
the user’s familiarity with it and what
they want to use it for; in other words,
the term “available” describes a rela-
tionship between the equipment, the
user and the task. Although availability
requires physical proximity to the user,
it is much more than this. Equipment
that is available as we use it allows us to
focus on what we want to do. This is in
contrast to equipment that gets in the
way of what we want to do, so that we
have to deal with the equipment first.
When the activity involves the need
to know about something, for example,
knowing what to do next, then a new as-
pect of availability is involved. Whereas
physical availability depends on a com-
bination of the physical design and
location of the equipment, the user’s
familiarity with it and what they want
to use it for, cognitive availability de-
pends also on the amount of interpre-
tation required to use the equipment.
This is trivial in the case of a hammer,
but not so in the case of computing ar-
tifacts. In order for computing artifacts
to support our focus on what we want
to do, they need to be both physically
available and cognitively available.
As the following discussion shows,
those within HCI have recognized that
the level of availability of the tradition-
al computer is a problem that needs
to be addressed. However, because no
distinction has been made between
physical and cognitive availability, the
proposed solutions do not adequately
address the issue of designing to im-
prove cognitive availability.
Both Weiser and Norman have criti-
an obvious physical move away from
acting in the world to ‘using’ the com-
puter. Mobile technology can bring the
computer to the person in the form of
laptops, handhelds and so on. How-
ever, as Figure 1 illustrates, mobility,
in and of itself, does nothing to remove
the dichotomy between reflecting on
the world and acting in the world.
We consider that Heidegger’s ac-
count of how we act in the world is a
truer account of everyday activity than
the deliberative theory of action implic-
it in Figure 1. According to Heidegger’s
situated theory of action, we are already
thrown into the world, continually re-
sponding to the situations we encoun-
ter. This means that in everyday activity
we seldom achieve the level of detach-
ment that allows us to make reflective
decisions before we act. Suchman7 im-
plicitly draws on Heidegger to argue
that, because we are absorbed in coping
with the present, we do not have time to
form a mental model about how to use
technology. This analysis has strongly
influenced HCI; however, it does not
fully address the problems with the tra-
ditional model of computing. In order
to articulate a model of computing ap-
propriate for the task of achieving Weis-
er’s vision of ubiquitous computing, we
must probe further into the situated
nature of action and draw explicitly on
Heidegger’s characterization of equip-
ment that is available.1 (The original
term ‘zuhandenheit’ is sometimes
translated as ready to hand.)
Heidegger describes as available
that equipment which helps us to deal
with the present without interrupting
the flow of absorbed coping. Equip-
ment that is available disappears from
our awareness. It is only when the
equipment doesn’t work as expected
that it is noticed. Heidegger gives the
example of a hammer that is too heavy
for the task of nailing a piece of wood.
In this case, the user’s attention is
drawn away from the task and to the
hammer itself; in particular, to the fact
that the hammer is too heavy. Because
the hammer is no longer available, the
user has to find another hammer or
find some unfamiliar way of using this
heavy hammer before they can proceed
with the task of nailing a piece of wood.
Whether equipment is available or not
depends on a combination of the de-
sign and location of the equipment,
cized the design of the traditional com-
puter as getting in the way of acting in
the world. Weiser says that the tradi-
tional computer “fails to get out of the
way of work… Rather than being a tool
through which we work, and so which
disappears from our awareness, the
computer too often remains the focus
of attention.”12 As Norman comments
in his book The Invisible Computer,6 ‘I
don’t want to use a computer, I want to
accomplish something.’
Norman’s focus, and that of HCI in
general, is on physical availability and
how the physical availability of arti-
facts can be increased through exploit-
ing physical affordances in the design
of the computing artefact.5 Exploiting
physical affordances goes some way to
increasing cognitive availability, but it
does not go far enough.
Furthermore, approaches under the
rubric of ‘ubiquitous computing’ have
generally also failed to address the is-
sue of improving cognitive availabil-
ity. For example, ‘anytime anywhere’
computing is a literal translation of
ubiquitous computing, emphasizing
access to the same information every-
where, whether by computers located
everywhere or users carrying a mobile
device. It is basically the traditional
model of computing on a grand scale.
Lyytinen and Yoo4 consider that the
problem with anytime, anywhere com-
puting is that the computing model
does not update as we move location.
In their work on pervasive computing,
they suggest that the way to make the
computer invisible is for the computer
figure 1: traditional model of computing takes us away from acting in the world

contributed articles
october 2009 | vol. 52 | no. 10 | communications of the acm 129
to automatically update its model of the
world from information it obtains from
the environment in which it is embed-
ded. However, although this overcomes
the need for unnecessary data entry, it
still does nothing to increase cognitive
availability. A computing artifact is still
not available if we have to turn our at-
tention away from what we are doing to
using the computing artifact.
In particular, having to interpret
a model of the world is disruptive to
the flow of situated action. It takes
the user’s attention away from what
they are doing to a model of the world.
This means that the user has to do in-
terpretive work to extract the relevant
information before proceeding with
what they were doing. Computing ar-
tifacts that rely on a representation of
the world are, by their nature, not cog-
nitively available. Delving more deeply
into Heidegger’s analysis of how we
are dynamically situated in the world
assists us to conceptualize more fully
how we can design technologies that
are cognitively available.
We have characterised Heidegger’s
analysis of the situated nature of ac-
tion as describing our state of being
thrown into the world and coping
with the present. However, as Figure 2
shows, there is also a future aspect to
our dealing with the present. Accord-
ing to Heidegger, we as human beings,
are simultaneously:
a) existing in the world with particular
interests (often translated as ‘thrown’);
b) absorbed in coping with the present
(often translated as ‘amidst’); and
c) pressing forward into future possibili-
ties (often translated as ‘projecting’).
This orientation toward the future
means that our everyday action in the
world is guided by what we perceive to
be the opportunities for action. We will
now show how we can build on this idea
to suggest a way of increasing the avail-
ability of computing artifacts. In this,
we draw from the findings of our proj-
ect to develop a radically new approach
to information system analysis and de-
sign, which is informed by the situated
theory of action.2,8 This work shows how
a situated approach to systems analysis
and design demands a focus on action
and how this focus on action leads to a
different understanding of how best to
provide information support. Unlike
traditional systems which are designed
first and foremost to provide informa-
tion for managing, the primary purpose
of situated systems is to
support routine action in
work systems.
Unlike traditional sys-
tems, the situated sys-
tems approach does not
propose to support action
by providing a representa-
tion of the world. Rather it
supports action by provid-
ing the actor with direct
access to the possibilities
for action (affordances)
present in the actor’s en-
vironment. Of course, in
this context, the affor-
dances relate to actions
which will help achieve the
goals of the work systems.
There are two aspects to
this support: making the
affordances present and
making the affordances
known. The first aspect
is realized through ma-
nipulating environmen-
tal structures to control
which actions are actu-
ally feasible for the actor.
The second aspect is realized through
indicating what actions are feasible. In
other words, the environment of the ac-
tor is manipulated so that only relevant
actions are possible and the actor is in-
formed that an action is possible with-
out needing to refer to a representation
of the state of the world.
The following applies these insights
from situated information systems to
the design of computing artifacts and
applications in order that ubiquitous
computing can be truly available to the
user. Rather than making the comput-
ing artifact/application itself the focus
of attention, design of ubiquitous com-
puting should centre on the follow-
ing two principles: making the possi-
bilities for action present and making
them known. On the one hand, mak-
ing the possibilities for action pres-
ent increases physical availability. In
contrast to previous work in HCI which
has focused on designing the artifact
so that it is likely to be more physically
available in use, this principle involves
manipulating environmental struc-
tures to control which actions are actu-
ally feasible for the user (so as to facili-
tate achievement of their purpose). On
the other hand, making the possibili-
ties for action known increases cogni-
tive availability. It involves indicating
to the user what actions are possible
in that place and that moment. In this
way, the attention of the actor remains
attuned to the action rather than being
diverted to a model of the world.
Some examples should make these
two principles clearer. Indeed, as men-
tioned at the outset, this new way of
conceptualizing how computing ar-
tifacts can best support activities is
already implicit in the design of some
applications considered to be part of
the ubiquitous computing vision. For
example, the first principle of the com-
puting artifact altering the structures
of the environment to control pos-
sible actions is implicit in the design
of smart spaces which manipulate the
action possibility space. These smart
spaces can adjust the lighting, tem-
perature, and airflow in response to
the numbers of people in the room and
so facilitate particular activities in the
room. Similarly smart security systems
respond to the detection of authorized
human beings and unlock doors to en-
able entry or exit.
figure 2: three aspects of how we are situated in the world

130 communications of the acm | october 2009 | vol. 52 | no. 10
contributed articles
designers to consciously design for
physical and cognitive availability.
Drawing from our work on developing
a situated approach to information sys-
tems analysis and design, we have pre-
sented two ways that ubiquitous com-
puting can be truly available – firstly,
through manipulating the space of
possible actions and secondly, through
indicating the possibility for action.
Only when there is a conscious effort
to design ubiquitous computing to be
both physically and cognitively avail-
able, will ubiquitous computing seam-
lessly support our everyday activities.
References
1. Dreyfus, H.L. Being-in-the-World. The MIT Press,
Cambridge, 1991.
2. Johnston, R.B., Waller, V. and Milton, S. Situated
Information Systems: Supporting routine activity
in organisations. International Journal of Business
Information Systems 1, 1/2, (2005), 53-82.
3. Lyytinen, K., Varshney, U., Ackerman, M.S., Davis,
G., Avital, M., Robey, D., Sawyer, S. and Sorensen, C.
Surfing the next wave: Design and implementation
challenges of ubiquitous computing environments.
Comm. of the Association for Information Systems 13,
(2004), 697-716.
4. Lyytinen, K. and Yoo, Y. Issues and challenges in
ubiquitous computing. Comm. ACM 45, 12, (2002),
63-65.
5. Norman, D. The Design of Everyday Things. Currency
Doubleday, New York, 1988.
6. Norman, D. The Invisible Computer: why good
products can fail, the personal computer is so complex,
and information appliances are the solution. The MIT
Press, Cambridge, MA, 1999.
7. Suchman, L.A. Plans and Situated Actions: the
problem of human machine communication.
Cambridge University Press, Cambridge, MA, 1987.
8. Waller, V., Johnston, R.B. and Milton, S. An action-
centred approach to conceptualising information
support for routine work. In Hart, D.N. and Gregor, S.D.
eds. Information Systems Foundations, Theory, Reality
and Representation. ANU Press Canberra, 2007, 171-
196.
9. Want, R. RFID: A key to automating everything.
Scientific American 290, 1, (2004), 46-55.
10. Weber, R. Ontological Foundations of Information
Systems. Coopers and Lybrand, Melbourne, 1997.
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12. Weiser, M. Some computer science issues in ubiquitous
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Vivienne Waller (vwaller@swin.edu.au) is a research
fellow at the Institute for Social Research, Swinburne
University of Technology, Melbourne, Australia.
Robert B. Johnston (robert.johnston@ucd.ie) is director
of the Centre for Innovation, Technology & Organisation
(CITO) and John Sharkey Professor of Information
Systems and Organisation at University College Dublin,
Ireland.
© 2009 ACM 0001-0782/09/1000 $10.00
The second principle of computing
artifacts indicating the possibility for
action is evident in a handheld navi-
gational aid that tells the user when
to turn (in other words, indicates the
possibility for a relevant action). Such a
navigational aid is likely to be more cog-
nitively available for a user who wants
to know when to turn than a handheld
navigational aid that depicts a map
which the user must interpret. Similar-
ly, there have been projects to develop
artifacts which alert the user when an
opportunity arises to interact with a
person who has similar interests.
When the two principles are applied
in a coordinated way, they have the
greatest effect in increasing the avail-
ability of ubiquitous computing. We
will base an illustration of this on Eric
Dishman’s work at Intel concerned
with finding ways to support people
with cognitive impairment.9 In this
example, the ubiquitous computing
artifacts assist through application of
the two principles: indicating the pos-
sibility of action and manipulating the
space of possible actions.
Imagine an older person is suffer-
ing episodes of mental confusion but
wants to remain living independently.
Active RFID technology can be used to
detect discrepancies in the execution
of simple tasks such as making a cup of
tea. When it is apparent that the person
is having trouble, the system provides
voice assistance as to what to do next.
Depending on the extent of confusion
inferred, further stages of assistance
can reduce the opportunity for danger-
ous actions; for example, automatically
locking kitchen cupboards that con-
tain household poisons.
As we have discussed, making ubiq-
uitous computing available is not lim-
ited to a single user. The concept can
be applied to the design of systems;
through informing and enabling ac-
tion, a network of devices can support
the coordination of time-constrained
operations in enterprises.8
Figure 3 summarizes what is need-
ed in order to achieve Weiser’s vision
of ubiquitous computing artifacts that
disappear from our awareness as we
use them. Because we are absorbed in
coping with the situations we encoun-
ter, ubiquitous computing artifacts
need to be designed for both physical
and cognitive availability. Because our
way of being orients us toward future
possibilities, physical and cognitive
availability involve an orientation to-
wards the future.
In the absence of articulation of
these conceptual guidelines to increase
the availability of computing artifacts,
research in ubiquitous computing has
proceeded in an ad hoc way and in a
variety of directions. Although increas-
ing cognitive availability is already im-
plicit in the design of some new tech-
nologies, other ubiquitous computing
technologies involve merely extending
the representational capabilities of the
computer. For example, despite the po-
tential of RFID technologies to inform
users about possible actions, there is
much work on RFID applications which
merely has the goal of widespread use
of RFID tags to associate objects with a
representation.
Existing technological capabilities
provide the potential to fulfil Weiser’s
vision. What has been needed is ar-
ticulation of concepts that will enable
figure 3: implications of the nature of being for the design of computing artifacts