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36 Chapter 2 Understanding and conceptualizing interaction

kinds of designs might be appropriate is, however, a skill that needs to be
learned. It is not something that can be done overnight through following a
checklist, but requires practice in learning to identify, understand, and examine
the issues-just like learning to write an essay or to program. In this chapter we
describe what is involved. In particular, we focus on what it takes to understand
and conceptualize interaction.
The main aims of this chapter are to:
Explain what is meant by the problem space.
Explain how to conceptualize interaction.
Describe what a conceptual model is and explain the different kinds.
Discuss the pros and cons of using interface metaphors as conceptual models.
Debate the pros and cons of using realism versus abstraction at the interface.
Outline the relationship between conceptual design and physical design.

2.2 Understanding the problem space
In the process of creating an interactive product, it can be temping to begin at the
"nuts and bolts" level of the design. By this, we mean working out how to design
the physical interface and what interaction styles to use (e.g., whether to use
menus, forms, speech, icons, or commands). A problem with trying to solve a de-
sign problem beginning at this level is that critical usability goals and user needs
may be overlooked. For example, consider the problem of providing drivers with
better navigation and traffic information. How might you achieve this? One could
tackle the problem by thinking straight away about a good technology or kind
of interface to use. For example, one might think that augmented reality, where
images are superimposed on objects in the real world (see Figure 2.1 on Color
Plate 2), would be appropriate, since it can be useful for integrating additional in-
formation with an ongoing activity (e.g., overlaying X-rays on a patient during an
operation). In the context of driving, it could be effective for displaying informa-
tion to drivers who need to find out where they are going and what to do at certain
points during their journey. In particular, images of places and directions to follow
could be projected inside the car, on the dashboard or rear-view mirror. However,
there is a major problem with this proposal: it is likely to be very unsafe. It could
easily distract drivers, luring them to switch their attention from the road to where
the images were being projected.
A problem in starting to solve a design problem at the physical level, therefore,
is that usability goals can be easily overlooked. While it is certainly necessary at
some point to decide on the design of physical aspects, it is better to make these
kinds of design decisions after understanding the nature of the problem space. By
this, we mean conceptualizing what you want to create and articulating why you
want to do so. This requires thinking through how your design will support people
in their everyday or work activities. In particular, you need to ask yourself whether
the interactive product you have in mind will achieve what you hope it will. If so,