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2.3 Conceptual models 39

Comment The problem space for this scenario was very open-ended. There was no identifiable problem
that needed to be improved or fixed. Alternatively, the new WAP technology provided op-
portunities to create new facilities and experiences for people. One of the main assumptions
is that people want to be kept informed of up-to-the-minute news (e.g. sports, stocks and
share prices) wherever they are. Other assumptions included:

That people want to be able to decide what to do in an evening while on their way
home from work (e.g., checking TV listings, movies, making restaurant reservations).
That people want to be able to interact with information on the move (e.g., reading
email on the train).
That users are prepared to put up with a very small display and will be happy browsing
and interacting with information using a restricted set of commands via a small number
of tiny buttons.
That people will be happy doing things on a mobile phone that they normally do using
their PCs (e.g., reading email, surfing the web, playing video games, doing their
shopping).

It is reasonable to assume that people want flexibility. They like to be able to find out
about news and events wherever they are (just look at the number of people who take a
radio with them to a soccer match to find out the scores of other matches being played at the
same time). People also like to use their time productively when traveling, as in making
phone calls. Thus it is reasonable to assume they would like to read and send email on the
move. The most troublesome assumption is whether people are prepared to interact with the
range of services proposed using such a restricted mode of interactivity. In particular, it is
questionable whether most people are prepared to give up what they have been used to (e.g.
large screen estate, ability to type messages using a normal-sized keyboard) for the flexibility
of having access to very restricted Internet-based information via a cell phone they can keep
in their pocket.

One of the benefits of working through your assumptions for a problem space
before building anything is that it can highlight problematic concerns. In so doing,
it can identify ideas that need to be reworked, before it becomes too late in the de-
sign process to make changes. Having a good understanding of the problem space
can also help greatly in formulating what it is you want to design. Another key as-
pect of conceptualizing the problem space is to think about the overall structure of
what will be built and how this will be conveyed to the users. In particular, this in-
volves developing a conceptual model.

2.3 Conceptual models
"The most important thing to design is the user's conceptual model. Everything else
should be subordinated to making that model clear, obvious, and substantial. That
is almost exactly the opposite of how most software is designed." (David Liddle,
1996, p. 17)