Accessibility means providing system infrastructure that allows add-on
assistive software to transparently provide specalized input and ouput
capabilities. For example, screen readers allow blind users to navigate
through applications, determine the state of controls, and read text via
text to speech conversion. On-screen keyboards replace physical
keyboards, and head-mounted pointers replace mice.

ATK, the Accessibility Tookit, is used to obtain accessibily information
from GTK+ and GNOME widgets.