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Chapter 2

Understanding and

conceptualizing interaction

2.1 Introduction
2.2 Understanding the problem space
2.3 Conceptual models
2.3.1 Conceptual models based on activities
2.3.2 Conceptual models based on objects
2.3.3 A case of mix and match?
2.4 Interface metaphors
2.5 Interaction paradigms
2.6 From conceptual models to physical design

Introduction
Imagine you have been asked to design an application to let people organize,
store, and retrieve their email in a fast, efficient and enjoyable way. What would
you do? How would you start? Would you begin by sketching out how the inter-
face might look, work out how the system architecture will be structured, or
even just start coding? Alternatively, would you start by asking users about their
current experiences of saving email, look at existing email tools and, based on
this, begin thinking about why, what, and how you were going to design the
application?
Interaction designers would begin by doing the latter. It is important to real-
ize that having a clear understanding of what, why, and how you are going to de-
sign something, before writing any code, can save enormous amounts of time and
effort later on in the design process. Ill-thought-out ideas, incompatible and un-
usable designs can be ironed out while it is relatively easy and painless to do.
Once ideas are committed to code (which typically takes considerable effort,
time, and money), they become much harder to throw away-and much more
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painful. Such preliminary thinking through of ideas about user needs and what

'User needs here are the range of possible requirements, including user wants and experiences.