Civil Engineering Reference
In-Depth Information
rather than cognitive theories. UPA organizes regular conferences to keep abreast with
developments in the field.
The International Standards Organization has published a famous standard, ISO 9241-
11. This standard defines usability as follows (ISO, 1995):
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.
Effectiveness refers to the accuracy and completeness with which users achieve specified
goals. Efficiency pertains to the resources expended in relation to the accuracy and
completeness with which users achieve goals. Satisfaction refers to comfort and
acceptability of use.
Over time the definition has seen many modifications. Nielsen (1994) specified five
characteristics of usability: ease of learning, efficiency of use, memorability (ease of
remembering), error frequency, and subjective satisfaction. Jordan (1998) was more
interested in the user's own experience of usability: guessability, learnability,
experienced user performance (EUP), system potential (optimum performance), and re-
usability.
Lately there has been a debate focused on “fun” in HCI. Things are fun, claims Carroll
(2004), when they attract, capture, and hold our attention by provoking new or unusual
perceptions, arousing emotions in context. They are fun when they surprise us, and
present challenges or puzzles as we try to make sense of them.
Carroll (2004) proposed a redefinition of usability to incorporate fun and other
significant aspects of user experience. According to Carroll this new concept should rely
on an integrated analysis of the
user's experience
. This is likely to lead to greater
technological progress, than merely itemizing a variety of complementary aspects of the
user's experience. The user experience is unified; it is a Gestalt impression. Users do not
decompose their impressions in terms of usability, aesthetics, and fun. Norman (2004),
who previously emphasized usability, is now quick to add that usable products that are
unattractive do not sell well. Emotions, aesthetics, and usability are indeed intertwined
(Helander and Khalid, 2005).
7.5
METHODS FOR USABILITY EVALUATION
Usability evaluations are conducted to identify the problems and difficulties experienced
in using software. There are two main categories of usability methods: analytical
evaluations and user-based evaluations.
Analytical evaluations are also called usability inspection methods. In this case the
product is evaluated by a professional analyst, such as a usability expert. There are three
common methods:
• Heuristics evaluation
• Cognitive walkthrough
• Model-based analysis such as goals, operators, methods, and selection (GOMS)
