Information Technology Reference
In-Depth Information
Usability for information visualization is about making techniques and
systems easy to understand and use, and fitting them closely to intended
users' needs and requirements. It may be defined in a variety of ways.
According to Nielsen and Mack:
Usability is a fairly broad concept that basically refers to how easy it is for
users to learn a new system, how efficiently they can use it once they have
learned it, and how pleasant it is to use; [2, p. 3]
while the International Organization for Standardization (ISO) definition
of usability is:
The extent to which a product can be used by specified users to achieve
specified goals with effectiveness, efficiency and satisfaction in a specified
context of use. [3]
The ISO definition, well known and commonly used in usability work,
consists of three aspects or dimensions of usability that can be assessed
during evaluation. Effectiveness refers to whether users can achieve their
objectives successfully with accuracy and completeness. Efficiency
assesses what effort and resource is expended in achieving those
objectives (e.g., time spent or mental workload). Finally, satisfaction deals
with how users feel about using a product, users' attitudes and preferences.
A basic concept of the ISO definition is that usability is not a property in
itself, but dependent on several aspects: different types of users (e.g.,
trained and experienced versus novices), their objectives when using a
product, and the context of use when they are active. These facts should
always be taken into consideration no matter what definition is used when
working with and assessing usability.
How do we know if an information visualization technique has good
usability? How do we know that it is appropriate and meaningful to users
performing tasks within the context in which they are supposed to be using
it? The answer is that evaluation is necessary.
Evaluation can be performed to assess any dimension of usability, it
can be performed at any stage of development, and there is a wide range of
methods proposed for use. Each method has its own requirements and
different methods uncover different usability issues. Some of them can
only be applied after the visualization technique has been implemented,
whereas others can also be applied in the early stages of design and
development. Thus, which technique to apply depends on the goal of the
evaluation study and the current state of development.
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