Summary: Putting It All Together - Foundations for Designing User-Centered Systems - page 398

and Chap. 13 on usability studies should provide you with a way to find out more
about particular users, particular tasks, or particular aspects of a task. There are
important topics not included here because of space, such as emotions, and these
you are now well equipped to learn on your own, or through further formal study
As you start to use and apply your knowledge of users to systems development,
you are likely to find that it leads you to raise several questions. When you address
these questions to human factors engineers, you will often find that their answer is
''It depends.'' If this topic has achieved nothing else, it should at least have helped
you to appreciate why ''it depends'': system performance is all about particular
people doing particular tasks in particular contexts, and those people are all dif-
ferent individuals, they have different skills and abilities, and they may work in
different physical, social, and organizational contexts.
The importance of appropriately integrating what we know about users into
system design is becoming increasingly widespread. The revised version of Boehm
and Hansen's ( 2001 ) incremental commitment model of system development, for
example, includes explicit consideration of users (Pew and Mavor 2007 ). The new
model provides a principled way for deciding when you need to know more about
your users. It explicitly acknowledges that not knowing enough about your users is
a risk to the successful completion of a system development project. If this lack of
knowledge about your users (their tasks and the context in which they work) poses
a significant risk, then you need to invest more time and effort in addressing those
issues until the risk is reduced to an acceptable level.
We have now shown you what sort of things you will need to know about your
users, and how to go about finding out that information. In doing so, we have
provided you with the foundations for designing user-centered systems.
14.6 Other Resources
Pew ( 2007 ) has written a history of models in this area. In it he provides a
summary as well as a description of the relationships between the various families
of models.
Salvucci has some nice models of how people drive (Salvucci 2006 ), and some
tools for predicting how secondary tasks will impair driving (Salvucci et al. 2005 ).
Byrne and Kirlik ( 2005 ) have provided similar lessons in aviation.
We have previously laid out a vision of future work that is needed to help
designers create models routinely (Ritter et al. 2003 ). It is available online and
notes about 20 projects that remain to be done with computational models of users.
Pew and Mavor's ( 2007 ) book is available on line, and you can purchase it or
register and download it. Their book provides useful pointers to a range of
methodologies for reducing the risks to system success that are caused by not
understanding users or their tasks. It could be and has been used to teach a separate
class on HCI methodologies. There was also a special issue of the Journal of
Cognitive Engineeringand Decision Making related to the topic published in 2008.