The term usability has several definitions in each research field.
In the field of Human–Computer Interaction (HCI) field, the most
widely accepted definition of usability is that proposed in the ISO
9241-11 [18]: ‘‘the extent to which a product can be used by specified
users to achieve specific goals with effectiveness, efficiency and satisfaction
in a specified context of use’’. This definition is that which
is closest to the human interaction perspective. In this view, usability
implies the interaction of users with the software product and
can be seen as the product’s capability to meet customer expectations.
On the other hand, in the field of Software Engineering (SE),
the most widely accepted definition of usability is that proposed in
the ISO 9126-1 [20]: ‘‘the capability of the software product to be
understood, learned, operated, attractive to the user, and compliant
to standards/guidelines, when used under specific conditions’’. In this
view, usability is seen as one specific characteristic that affects the
quality of a software product. It can be evaluated during the early
stages of Web development and does not necessarily imply the
user’s interaction with the system since it can be measured as
‘‘conformance to specification’’, where usability is defined as a
matter of products whose measurable characteristics satisfy a fixed
specification which has been defined beforehand. These different
definitions of usability directly affect how it is evaluated, since
each method or technique employed in these evaluations may focus
on different aspects of the term usability (e.g., effectiveness of
user task, learnability of user interfaces).