User-Centered Systems Design: A Brief History - Foundations for Designing User-Centered Systems - page 45

Table 2.1 Principles for design to avoid exasperating users (Hedge 2003 )
• Clearly define the system goals and identify potential undesirable system states
• Provide the user with appropriate procedural information at all times
• Do not provide the user with false, misleading, or incomplete information at any time
• Know thy user
• Build redundancy into the system
• Ensure that critical system conditions are recoverable
• Provide multiple possibilities for workarounds
• Ensure that critical systems personnel are fully trained
• Provide system users with all of the necessary tools
• Identify and eliminate system ''Gotchas!''
provided, and that the system should be consistent across its subsystems. Similarly,
Hedge ( 2003 ) offers the principles shown in Table 2.1 .
Guidelines are prescriptive and offer some general guidance for making design
decisions. They tend to be more specific than principles, but still relate existing theory
and knowledge to either new design or established design problems (e.g., Brown
1988 ; Mosier and Smith 1986 ; or the Apple design guidelines, available online).
Below we offer a number of principles and guidelines that we have found useful in our
own work. In designing and evaluating systems we ask questions about the design's
functionality, usability, learnability, efficiency, reliability, maintainability,andutility
or usefulness. These are all discussed below.
(1) Functionality, what something does, is often the first thing to be considered
while consideration of usability issues is sometimes tacked on at the end of
development. This can lead to poorly designed artifacts that are hard to use but that
offer new functionality. Sometimes this is enough. Sometimes it is not. Often, with
more thoughtful design, one can have both (Pew and Mavor 2007 ).
(2) Usability is a complex concept that can be defined in several ways. For
example, Ravden and Johnson ( 1989 ) specify the following as all relevant to an
assessment of whether a system or technology is usable or not:
Visual clarity
Consistency
Informative feedback
Explicitness
Appropriate functionality
Flexibility and control
Error prevention and control
User guidance and support.
Eason ( 1984 ) offers the following definition of usability: the ''major indicator of
usability is whether a system or facility is used.'' However, this is patently not the
case as many devices that are used are hard to use. More usefully, Eason notes that
usability is not determined by just one or two constituents, but is influenced by a