Biomedical Engineering Reference
In-Depth Information
For Federici and Borsci (2010), according to the integrated model, accessibility and usabil-
ity do not refer to the objective and subjective factors of the user/technology relationship,
but rather to a bidirectional way of observing the interaction. Actually, this represents two
outlooks from which the one and only observed reality of the user/technology system is
drawn. Accessibility of an environment is therefore defined based on how it allows the
user to initiate and terminate the operation that completes the machine's task (functioning
construct), whereas its usability is based on the user's perception of the user/technology
interaction (user performance). The functioning construct of a system is the basis for stan-
dard rules (e.g., Web Content Accessibility Guidelines) against which accessibility levels
are controlled and assessed. The user performance in relation to the functioning construct
of a machine allows us to deduce scales (e.g., efficiency, satisfaction, cognitive load, and
helpfulness) of usability scores.
The object of the evaluation cannot be merely reduced to the artifact or to the user:
what is to be evaluated is the functionality of the intrasystemic dialogue between the
user (i.e., the subjective dimension of the interaction) and interface (i.e., the objective
dimension of the interaction). The accessibility and the usability estimations, then,
need to be understood as the measurements of the possibility for the user to achieve
their goals navigating the given interface. The evaluation of the intrasystemic relation
between user and technology includes object-oriented methods as well as subject-
oriented ones; still, the overall evaluation cannot be obtained by the simple addition of
the results coming from the two different methods but by an evaluation process able to
consider and integrate both the accessibility and usability dimensions. An integrated
model of usability evaluation is compatible with a universal model of disability whereby
ability/disability are viewed within a continuum. Using ability/disability to refer to an
individual functioning in a real context can only have a theoretical interest because
nobody has a complete absence of disability or complete absence of ability (Zola 1989;
Bickenbach et al. 1999; WHO 2001). Therefore, ability/disability are referred to by the
activities performed by an individual, originating from the environment and valued by
a predetermined functioning construct. These activities can change the topology of an
environment, and the construct with respect to the process and measure expected of
its functioning.
The model proposed by Federici and Borsci (2010) is based on the UX framework and on
the idea that UX problems are originated by a distance between the models
used to reason
about the system, to anticipate its behaviour and to explain why it reacts as it does
(Craik
1943) by the designer of the technological product and by the user of the product. Mental
models, considered according to Norman's (1983) definition of “system causality convey-
ance,” are those collections of knowledge and skills that lead the subject in the interaction
(user) or in the creation (designer) of an interface. From the point of view of the evaluation
process, we need to consider that
•
The developer's cognitive processes
involved in the design of the system are mostly
connected to problem-solving strategies, to the representation of knowledge, and
to expertise in complex task environments. Although these processes have been
analyzed deeply, the difficulties due to the “simulation” process have never been
properly studied in depth. When designing an interface, the developers simulate
how a user would perform to achieve their goals; therefore, the designer devel-
ops the functions of the system according to their idea of a potential user and
of a hypothetical interaction. Furthermore, there are many stakeholders involved
