Some of Norman's stages correspond roughly to Foley et a1.'s separation of
concerns; that is, the user forms a conceptual intention, reformulates it into the
semantics of several commands, constructs the required syntax, and eventually
produces the lexical token by the action of moving the mouse to select a point on
the screen. Norman makes a contribution by placing his stages in the context of
cycles of action and evaluation. This dynamic process of action distinguishes Norman's
approach from the other models, which deal mainly with knowledge that
must be in the user's mind. Furthermore, the seven-stages model leads naturally
to identification of the gulf of execution (the mismatch between the user's intentions
and the allowable actions) and the gulf of evaluation (the mismatch between
the system's representation and the user's expectations).
This model leads Norman to suggest four principles of good design. First, the
state and the action alternatives should be visible. Second, there should be a
good conceptual model with a consistent system image. Third, the interface
should include good mappings that reveal the relationships between stages.
Fourth, users should receive continuous feedback. Norman places a heavy
emphasis on studying errors, describing how errors often occur in moving from
goals to intentions to actions and to executions.
A stages-of-action model helps us to describe user exploration of an interface
(Polson and Lewis, 1990). As users try to accomplish their goals, there are four
critical points where user failures can occur: (1) users can form an inadequate
goal, (2) users might not find the correct interface object because of an incomprehensible
label or icon, (3) users may not know how to specify or execute a
desired action, and (4) users may receive inappropriate or misleading feedback.
The latter three failures may be prevented by improved design or overcome by
time-consuming experience with the interface (Franzke, 1995).
Refinements of the stages-of-action model have been developed for other
domains. For example, information-seeking has been characterized by these
stages: (l) recognize and accept an information problem, (2) define and understand