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40 Chapter 2 Understanding and conceptualizing interaction

By a conceptual model is meant:
a description of the proposed system in terms of a set of integrated ideas and concepts
about what it should do, behave and look like, that will be understandable by the users
in the manner intended.
To develop a conceptual model involves envisioning the proposed product, based
on the users' needs and other requirements identified. To ensure that it is designed
to be understandable in the manner intended requires doing iterative testing of the
product as it is developed. A key aspect of this design process is initially to decide
what the users will be doing when carrying out their tasks. For example, will they
be primarily searching for information, creating documents, communicating with
other users, recording events, or some other activity? At this stage, the interaction
mode that would best support this needs to be considered. For example, would al-
lowing the users to browse be appropriate, or would allowing them to ask questions
directly to the system in their native language be more effective? Decisions about
which kind of interaction style to use (e.g., whether to use a menu-based system,
speech input, commands) should be made in relation to the interaction mode.
Thus, decisions about which mode of interaction to support differ from those
made about which style of interaction to have; the former being at a higher level
of abstraction. The former are also concerned with determining the nature of the
users' activities to support, while the latter are concerned with the selection of
specific kinds of interface.
Once a set of possible ways of interacting with an interactive system has been
identified, the design of the conceptual model then needs to be thought through
in terms of actual concrete solutions. This entails working out the behavior of the
interface, the particular interaction styles that will be used, and the "look and
feel" of the interface. At this stage of "fleshing out," it is always a good idea to
explore a number of possible designs and to assess the merits and problems of
each one.
Another way of designing an appropriate conceptual model is to select an in-
terface metaphor. This can provide a basic structure for the conceptual model that
is couched in knowledge users are familiar with. Examples of well-known interface
metaphors are the desktop and search engines (which we will cover in Section 2.4).
Interaction paradigms can also be used to guide the formation of an appropriate
conceptual metaphor. They provide particular ways of thinking about interaction
design, such as designing for desktop applications or ubiquitous computing (these
will also be covered in Section 2.5).
As with any aspect of interaction design, the process of fleshing out conceptual
models should be done iteratively, using a number of methods. These include
sketching out ideas, storyboarding, describing possible scenarios, and prototyping
aspects of the proposed behavior of the system. All these methods will be covered
in Chapter 8, which focuses on doing conceptual design. Here, we describe the dif-
ferent kinds of conceptual models, interface metaphors, and interaction paradigms
to give you a good understanding of the various types prior to thinking about how
to design them.