Biomedical Engineering Reference
In-Depth Information
2010, p. 9). In this sense, “Web accessibility” means that “people with disabilities can use
the Web […] more specifically [they] can perceive, understand, navigate, and interact with
the Web” (WAI 2006). Di Blas and colleagues state that “W3C guidelines only guarantee
'technical readability,' i.e., the very fact that screen readers can work; they do not ensure at
all the fact that the Website is 'accessible' by blind users, in the sense that blind users can
effectively access it.” (2004, p. 1).
These authors underline that the most important aim of the World Wide Web Consortium
(W3C) is to ensure an effective user experience, or “usable accessibility” (Di Blas et al. 2004).
However, it is interesting that accessibility has a less comprehensive definition whereas
it has a more defined and shared method of assessment than usability. Indeed, accessibility
focuses on the objective analysis of the system through the conformance to international
guidelines, whereas the usability evaluation does not have a unified and shared method-
ology. The usability evaluation focuses on the users' achievement of the goal regarding
effectiveness and efficiency and on their satisfaction, and it results in a more subjective,
and so less reducible, characteristic for assessment. This difference in evaluation between
accessibility and usability turns in an impressive set of reliable and valid evaluation meth-
ods for usability.
Despite the differences among the evaluation objectives, the concept of accessibility and
usability are inter-related because they are two ways to detect interaction problems from
different angles. As Petrie and Kheir emphasized, accessibility and usability problems
can be seen as two overlapping sets, which would include three categories as follows (see
Figure 15.2):
[i] Problems that only affect disabled people; these can be termed “pure accessibility”
problems; [ii] Problems that only affect non-disabled people; these can be termed “pure
usability” problems; [iii] Problems that affect both disabled and non-disabled people;
these can be termed “universal usability”
problems. Accessibility problems were not a
complete sub-set of usability problems. (2007, p. 398; please see also Shneirderman 2003;
Horton 2007; Lazar 2007).
In this sense, accessibility problems are not the subset of usability problems, nor are
usability problems the subset of accessibility problems.
15.2.2 An Overview of the Usability Standards
Organizations in charge of international standardization include the International
Organization for Standardization (ISO), the International Electrotechnical Commission
(IEC), and the Comité Européen de Normalisation (CEN). In addition to these, there are
local organizations such as Japanese Industrial Standards (JIS), Deutsches Institut für
Normung (DIN), British Standards Institute (BSI), and American National Standards
Institute (ANSI). They have issued many standards and documents in terms of usability
and accessibility, sometimes in conjunction with each other. Usually, international stan-
dards are established first, and some of them will be translated as local standards. But
sometimes local standards become international standards, as in the case of JIS X8341-1
(2006) and ISO 9241-20 (2009).
Regarding usability, many standards and documents were published by the Technical
Committee (TC) on the ergonomics of ISO (see http://www.iso.org). In the ISO/TC159, there
are four Subcommittees (SC), i.e., SC1, SC2, SC3, and SC4, in which SC4 is in charge of the
“Ergonomics of Human-System Interaction.” In SC4, there are 11 Working Groups (WG),
in which WG6 is in charge of “Human-Centered Design Processes for Interactive Systems.”
