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The ISO has also fairly recently developed checklists based on standards and principles of user guidance
and dialog as subsets of the overarching ISO 9241 Standard on Ergonomics Requirements for Visual
Display Terminals (ISO, 1998). Sample checklists associated with these standards are provided by
Stewart and Travis (2003) in their chapter on “Guidelines, Standards, and Style Guides” in Jacko and
Sears' (2003), The Handbook of Human-Computer Interaction.
In addition to these international standards, there are several other sets of guidelines that have been
established by developers, HCI researchers, and usability professionals (e.g., Apple Computer, 2003;
Microsoft Corporation, 2004; W3C, 2004). With so many standards and legal requirements promoting
accessibility, designers must have guidance in how to incorporate these requirements into the main-
stream UCD process. A comprehensive review of accessibility, universal design standards, and techniques
for how to meet these requirements can be found in work by Preiser and Ostroff (2001).
However, unless the design team has a substantial portfolio of experience in a specific design domain,
the translation of specifications into tangible systems is typically a challenge, for which there is little gui-
dance (Ostroff, 2001). That being said, a more effective approach is the generation of several design
alternatives and creating low-fidelity mock-ups of these alternatives. Through testing and evaluation,
the design alternatives are evaluated to verify the degree to which they address the initially derived
requirements. Based on the evaluation, designs are altered and iteratively evaluated with prototypes of
increased fidelity until the final optimal design is ready for implementation.
7.3.2.6.5 For Consideration in UCD: Principles of Usable Design
Even after the implementation of a design, the process of UCD continues. Alterations and adjustments
are continually integrated into the system based on the need to optimize the compatibility of the user-
system interaction as both evolve relative to the other over time (Karwowski, 2003). Seemingly endless
variations of this conceptualization of UCD exist in the literature under several guises such as the usabil-
ity engineering lifecycle (Mayhew, 1999), contextual design (Beyer and Holtzblatt, 1998), compatible
design (Karwowski, 2003), and others. Nonetheless, at the core of each approach lies an ideology of estab-
lishing a conscious awareness of users, context, and work.
That said, the system design and its implementation must place emphasis on derived usability goals,
the environment, task, workflow, and characteristics of the user (cognitive and physical). As the users and
system are evolving and dynamically interrelated, UCD must reflect this propensity for change. This is
accounted for in the cyclical pattern of UCD and the iterative appraisal of the systems, users, and work to
best preserve productivity and success.
Many, including Norman (1988, 2002) formulated general design guidelines that are universal to any
usable design and serve as the underlying goals of UCD. Examples include Norman's seven principles of
design, Shneiderman's eight golden rules of design (Norman, 2002; Shneiderman, 1998), and Nielson's
design heuristics (Nielsen, 1994), summarized in Table 7.5. Additionally, there are several additional
principles of design spanning across the disciplines of art, design, natural science, psychology, and
more (see Lidwell et al., 2003, for an extensive review). Common to all of these guidelines is the pur-
ported need to consider these rules in light of the actual user's needs, desires, and individual differences
taking into account who the users are, what they do, and where they do it.
However, since the preliminary introduction of these guidelines in the mid 1980s, there are innumer-
able guidelines published as the outcome of research, practice, and the emergence of new technologies.
Furthermore, these guidelines typically do not become obsolete. Recently, Nielsen (2005) reviewed the
present-day relevance of 944 usability guidelines published in an 1986 Air Force documentation on
usability knowledge and guidelines for the design of military command and control centers. In his
appraisal, Nielsen determined that 70% of these guidelines were fully applicable to present-day
systems. The majority of those irrelevant guidelines were less important due to the anticipated obso-
lescence of certain design elements and technologies.
For designers this poses a problem of information overload. One cannot possibly fully address all guide-
lines as it takes a vast amount of time and money to accomplish and it is also likely that there will be
some contradiction between guidelines. Through UCD, designers must apply knowledge about the
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