Databases Reference
In-Depth Information
CHAPTER
5
Non-Visual Interfaces
Usability and visual interfaces are key issues, but, if we want to enlarge the user categories that data
management systems are addressing, we must broaden the user-centered approach described so far,
moving towards the so called
universal access
or
universal usability
.
Universal access refers to the requirement of coping with diversity in: (1) the characteristics
of the target user population (including people with disabilities); (2) the scope and nature of tasks;
and (3) the different contexts of use (
Stephanidis and Savidis
,
2001
). Shneiderman instead proposes
“universal usability” as a term to encompass both accessibility and usability, but notes that “access
is not sufficient to ensure successful usage” (
Shneiderman, B.
,
2000
). He defines a different ranking
of accessibility in comparison to usability: accessibility is a first but not sufficient requirement to
achieve universal usability.
5.1
ACCESSIBILITY
The accessibility issue for visual interfaces is gaining increasing interest, mainly driven by web
diffusion, and several research activities deal with standards and methodologies for enforcing it (see,
e.g., the Web Content Accessibility Guidelines (
WCAG
,
2008
)).
Accessibility is an increasingly relevant concern for data access as well because the accommo-
dation of the needs of the user with various disabilities is a definite requirement, especially when
data are the result of a public effort. In the following, we focus on a particular kind of disability:
visually-impaired users, because they impose a serious reflection on the way a visual user interfaces
are designed. In fact, whilst character-based interfaces offer blind people the extraordinary possibility
to make use of their skills in using keyboards and interacting with software tools, graphic interfaces
are difficult to manage in an oral interaction. Visual interfaces, in fact, usually imply complex page
layouts, many visual features and, above all, the use of the mouse has made their use a difficult and
cumbersome task.
Visually-impaired people currently access visual interfaces (e.g., web interfaces) using screen
readers, that is, software tools capable of interpreting the HTML code and reading it aloud (with a
synthesized voice); interaction is allowed by the use of Braille keyboards or through a combination
of key-strokes on the traditional keyboards. The worth of screen readers is clear; nonetheless, their
limits are also recognized and discussed in literature (
Theofanos and Redish
,
2003
):
They read everything, including elements of HTML that are only useful for visualization (and
do not convey relevant meaning to the listener).
