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CHALLENGES FOR DESIGNING TANGIBLE SYSTEMS
In this section we aim to outline some of the problems and
challenges which raise during the process of design and
interaction with tangible user interfaces. Based on the previous
work and our own experience, we discuss the following
aspects of tangible systems: (1) scalability, (2) acceptability,
(3) novelty and complexity of interaction, (4) form factor and
context of use and (5) maintenance and complexity. In the
following we discuss in detail each of the aforementioned
dimensions.
Scalability
Designers of new tangible systems are often trying to
maximize the scalability of a system they are developing. In some
cases this is needed to enable the use of the system by multiple
users or to integrate different modalities into an artifact.
However, the level of a scalability is still limited in comparison to
a smartphone application, and often increases the complexity
of a tangible system. Couture et al. [
3
], for example, studied
whether a tool with a generic form factor can be scaled and
substitute tools with a dedicated functionality. However, systems
that support an extension of contacts [
5, 20
], different kinds of
notifications [
1
] or modalities [
8
] still have an extension limit.
The questions that are raised: “What happens if the number of
communication partners increases to 100?" or “What if I have
five types of notifications instead of one? Do I want to have
five notification objects on my desk?" Matviienko et al. [
11
]
tried to solve this issue with a tangible modular calendar by
letting the users assign and reassign a contact to a dedicated
tangible figure. Even though these artifacts have been
developed with a possible scalability in mind, they are still restricted
in comparison to most software systems. The extension of
tangible systems in comparison to smartphone applications
is demanding more resources and is harder to realize in the
late stages of the development process. One of the research
questions to explore in the future work would be: “How can
we design tangible systems with simplified scalability?"
Acceptability
Acceptability and integration of new tangible systems in
people’s environment is another challenging aspect for designers
and developers. Systems which are designed in the form of a
flower [
20
], a tree or a house are not immediately accepted,
if at all. Even though people are used to tables and desks
in their working environments, the artifacts in the form of a
table [
19
] would require some time for a user to get used to it.
Moreover, people get often attached to specific artifacts from
their environment, since they inherit memories from their past
[
2
]. When designing artifacts that replace existing objects, it is
important to involve users into the design process or integrate
existing objects into the design.
Users who use portable tangible systems, such as CubeLendar
[
12
] or Forget-Me-Not [
20
], often face problems of
acceptability, since taking an object to a location uncommon for the usual
interaction might raise social concerns or is annoying to the
users. It is a long process of accepting and adapting to a new
tangible artifact in the environment, especially when designed
to be used in various contexts of use. For example, an artifact
which has been designed for domestic environment might not
fit into a workplace. As a consequence, users tend not to use
the systems in different context. It affects users’ interaction
with a system and can provide misleading information in field
experiments.
Another challenging aspect regarding future tangible system is
to investigate the change of interaction with the same
functionality developed as a mobile application and as a tangible object.
Users usually do not face problems using new applications on
their smartphone, but need time to get used to new tangible
systems. What is missing in tangible objects for increasing
their acceptability? This leads us to another research question:
“Which properties of tangible objects can help increasing users’
acceptance?"
Novelty and Complexity of Interaction
Different software applications imply interaction with the
same physical object, e.g. smartphone or laptop. The
interaction paradigm for software systems is often consistent
due to standards and best design practices. Tangible artifact,
however, have various form factors. Therefore, a user has
to learn an interaction for a specific object and adapt to its
affordances. Ullmer et al. [
17, 16, 15
], however, tried to
solve this issue by presenting physical interaction elements
which can serve common roles across different tangible
systems. Furthermore, physical objects are not mutable, and are
not able to change their physical representation as it would be
possible with digital systems, e.g., change a button state [
13
],
undo or a history function [
10
]. This can be a challenging
aspect, especially when designing for non-technical users like
children or elderlies. To reduce complexity of the interaction
and to ease the way users are interacting with an artifact,
designers of tangible systems have to carefully select solutions
and involve users as early as possible into the design process.
This might include brainstorming sessions to get insights into
users’ needs, low-fi prototyping sessions together with users
to get early feedback on form and size of tangible artifacts and
continuous user evaluations within a realistic context of use.
Another research questions to explore here would be: “How
can we design tangible systems with minimized novelty effects
and complexity of interaction?"
Form Factor and Context of Use
Some of the tangible systems are restricted to the environments
where they can be used. The form factor of a tangible artifact
is one of the reasons. If one uses an ambient light on the lamp
[
4
] to encourage people to move more at work, she cannot take
it home as easily as a smartphone with a fitness application
installed on it. The systems such as the information percolator
[
6
] is a stationary system integrated into environment, which
can function and show information in the environment, where
it was installed. Other examples like the StoryBox [
18
] can
be used to support children and elderlies to easily create and
share stories within a domestic context. Due to the interaction
concept, the box has certain form factor constraints with
regards to its size, and relatively large size might not be accepted
by all users within their homes. Therefore, the form factor of
tangible systems might restrict the context of use and often
raises acceptability concerns by users, especially when used
within a domestic context. The designers of tangible artifacts
should further not only consider affordances through physical
shape, but also take ergonomics into account, which are
especially important for longer-term usage of systems. This leads
us to another research question: “How can we design tangible
systems with a flexible context of use?"
Maintenance and Complexity
After all, maintaining tangible systems for research purposes
is cumbersome in comparison to software applications. When
such applications fail, a researcher can update the software
remotely or provide an exchange device with an updated
application. When a tangible system fails, one has to either fix
the whole system or as in the case with smartphone
application provide a new one. However, building a new tangible
system as back-up is more time and costs consuming than a
pure software application.
A tangible system usually consists of a multiple hardware
components. These components have to communicate with
each other by exchanging data to ensure that a system works as
one module. The more components are integrated in a tangible
system, the higher its complexity, the harder its maintenance.
Another research question here would be: “How can we design
tangible systems with a simplified maintenance?"
CONCLUSION
We presented some of the challenges in the application of
designing and developing new tangible systems from our own
experience and from other related works. The design and
evaluation of tangible interfaces with users in a realistic
environment can be challenging and requires a lot of attention
by researchers and designers. Although, this is an important
topic, these challenges rarely get reported or reflected after
an artifact has been designed and implemented into the field.
This work is far from being conclusive, but rather is meant to
create starting points for discussion. We hope that reporting
some of the challenges will assist future designers of tangible
systems and avoid the identified issues.