Biomedical Engineering Reference
In-Depth Information
is an evident interrelation with the concept of accessibility expressed in some national
and international definitions of accessibility, such as Section 508 of the U.S. Rehabilitation
Act of 1973 (e.g., see the web site for understanding and implementing the requirements
of Section 508, http://www.section508.gov), the JIS X8341 series in Japan, and the defini-
tions of WAI, which found in the usability standards an application. The relation between
accessibility and usability is clearly expressed in ISO/IEC Guide 71 (2001), which expresses
the standard that takes into account the needs of older persons and persons with disabili-
ties in the interaction, in ISO 9241-20 (2009), which described the accessibility guidelines
for information/communication technology equipment and services, and in ISO 9241-171
(2008), which proposes guidance on software accessibility.
The relationship between usability and accessibility is particularly evident in the ISO/
IEC Guide 71 (2001), in which it is recognized that accessibility and usability are important
for both products and services because “some people with very extensive and complex dis-
abilities may have requirements for access to the product.” This guide
Describes a process by which the needs of older persons and persons with disabilities
may be considered in the development of standards; provides tables to enable standards
developers to relate the relevant clauses of a standard to the factors which should be
considered to ensure that all abilities are addressed; offers descriptions of body func-
tions or human abilities and the practical implications of impairment; offers a list of
sources that standards developers can use to investigate more detailed and specific
guidance materials. (ISO 2001).
As we have seen in this section, the inter-relation between accessibility and usability con-
cepts is clearly marked by both the standards and the UX theoretical approach. Although
this relation is evident, practitioners are accustomed to doing a split in the evaluation pro-
cess of products in two uncorrelated steps: the evaluation of accessibility and the evaluation
of usability. In these two steps, the accessibility represents the evaluation of the objective
access to the interaction, as the measure of the way the architecture accomplishes the stan-
dards (i.e., objectivity), and the usability represents the evaluation of the subjective use of
the interaction (i.e., subjectivity). This strong division between objective and subjective
aspects of interaction is a limitation of the UX studies that can be recomposed only by an
integrated model of interaction evaluation (Federici and Borsci 2010).
15.3 Evaluation of Systems
15.3.1 A Conceptual Framework: An Integrated
Model of Interaction evaluation
The relation between accessibility and usability, as we claim, is often reduced superficially
to that of objectivity and subjectivity (Federici et al. 2005; Federici and Borsci 2010). However,
this simplification does not catch all of the aspects involved in the interaction between
technology and user (Annett 2002; Kirakowski 2002). As Federici and Borsci claim,
Accessibility refers to the interface code that allows a user to access and achieve the
information (e.g., a user can read a text alternative description of a figure by a screen
reader), usability pertains to the subjective perception (satisfaction) of the interface struc-
ture's efficiency and effectiveness (e.g., a user is satisfied because they can immediately
