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2.2. Review of Existing Development Processes
19
GOMS model (Goals, Operators and Selection Rules).
[
Card et al. 1983
]
postulates that users formulate goals and sub-goals, whereof each can be reached by
the use of methods and procedures. Selection rules are the control structures of the
selection from the various methods to reach the goal. Additionally, a so-called key-
input model predicts times for the error-free fulfilment of tasks performed by experts.
Both models focus on experts neglecting errors, problems, and user satisfaction.
Seven Stages of Action.
[
Norman 1988
]
proposes a model for human-computer
interaction: (1) Forming the Goal, (2) Forming the Intention, (3) Specifying an Ac-
tion, (4) Executing an Action, (5) Perceiving the State of the World, (6) Interpreting
the State of the World, and (7) Evaluating the Outcome.
Eight Golden Rules of Interface Design.
[
Shneiderman 1997
]
introduces a
collection of principles that are derived heuristically from experience. They are
applicable in most interactive systems after being properly refined, extended, and
interpreted: (1) Strive for consistency, (2) Enable frequent users to use shortcuts, (3)
O er informative feedback, (4) Design dialog to yield closure (inputs are grouped,
end of dialog is obvious), (5) O er simple error handling, (6) Permit easy reversal
of actions (undo), (7) Support internal locus of control (user keeps control), and (8)
Reduce short-term memory load (user doesn’t have to remember info).
Discussion
The collection of principles above gives but a short overview about the main guide-
lines and ‘golden rules’ in HCI. Apart from that, there exists also a variety of ap-
plicable graphical user-interfaces concepts, such as direct manipulation, selection
menus, input fields, command language, and natural language. All these heuristics
and techniques provide developers with a rich knowledge base and frameworks about
how to develop well-designed user-interfaces. However, the appropriate application
of those frameworks and theories has to be part of development processes.
2.2.4 User-Centered Design
The objective of user-centered design
[
Norman and Draper 1986
]
is to create optimal
functioning human-machine systems. Instead of backing-up from theories, the user
becomes part of the process, at least to a certain extend. As such, the focus of
user-centered design is on the the goals, tasks, and needs of the user instead of
technological constraints. This challenges developers to shape the user-interface
around the capabilities and needs of the user. Accordingly, user-centered design
provides methods to incorporate user inputs during the requirements phase. Most
of these practices are built on the hypothesis-testing model of traditional empirical
research. User-centered design can be done for users, by users, and also together with
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