This W3C Draft Note describes profiles of
some users in the Web community with disabilities and some
browsing tools at their disposition. This document is
intended to provide Web content developers and Web tool developers with
information complementary to the WAI Accessibility
Guidelines.
This document is [Not yet] a W3C Note made available by the W3C
and the W3C Web Accessibility Initiative. This NOTE has [not yet]
been jointly approved by the WAI Education and Outreach Working Group (EOWG)
and Protocols and Formats Working Group (PFWG).
Publication of a W3C Note does not imply endorsement by the W3C membership.
A list of current W3C technical reports and publications, including working
drafts and notes, can be found at http://www.w3.org/TR.
NOTE: This document has been modified after its original date of publishing
to correct the "Latest Version" URI.
For organizational purposes, profiles have been organized into three broad
classes: sensory, physical, and cognitive.
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Low vision
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There are many types of low vision, including poor acuity, tunnel vision,
clouded vision, floaters in the eye, peripheral vision, etc. Some people
with low vision need to enlarge the text fonts and images, and may use use
a dual (i.e., partial) or full screen magnifier.
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Note. Low vision users may still encounter difficulty
deciphering information on the computer screen even when magnified due to:
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magnifying small fonts or images may cause pixelation and/or distortion
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magnified areas tend to loose contextual information (tunnel vision effect
doesn't allow user to "see" what information or choices are around the magnified
area).
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Blindness
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People are legally blind when they have less than 20/200 vision in the better
eye after correction, or less than a 20 degree field of view in the better
eye after correction. Individuals who are blind rely primarily on screen
readers to read the text on the screen. For graphic elements, they rely on
the presence of a text description of the image (and any text that is included
as an image in the document).
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Hard of hearing
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A person whose hearing is less severely impaired than deafness is said to
be hard of hearing.
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Deafness
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A person is considered deaf when sound must reach at least 90 decibels to
be heard at all and even amplified speech cannot be understood. Normal
conversation is approximately 40 to 60 decibels.
There is a tremendous variety of physical disabilities. In addition to the
usual range from minor to severe involvement, there are also many different
types of physical disabilities. In order to better understand its breadth,
it is useful to break this category into two major areas: neuromuscular and
skeletal. Neuromuscular impairments include any impairments that relate to
the nervous system (including the brain) or the muscles. For example, most
speech impairments fall into this area. Skeletal impairments relate to the
bones, joints and missing limbs.
Although there are many specific types of neurological impairments, their
effects can be characterized as variations or combination of:
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Paralysis
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This lack of any muscular control and often sensation in part of the body.
This is usually caused by a break in the nerves leading to the muscle, often
in the spinal cord.
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P aresis
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Weakness or inability to produce small, controlled or forceful movements.
This can be caused by problems with the signals sent to the muscles via the
nerves, problems with the muscles themselves, or problems due to pain when
movements are made (as in the case of severe arthritis).
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Interference with Control
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This interference can take different forms. The term spasticity is used if
the muscles are tense and contracted and voluntary movements is very difficult.
Ataxia refers to problems in motor programming and coordination. Athetosis
and Chorea refer to constant or uncontrolled motion (i.e., extra, involuntary
movements).
These disabilities result from some type of damage to the human brain. Therefore
it is not surprising that there is a great complexity of impairments in this
category. Cognitive disabilities can be divided into the following seven
categories:
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Impairments of Intelligence and Thinking (e.g., Mental Retardation, Dementia).
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Impairments of Memory (e.g., Amnesia, Memory illusions, Forgetfulness)
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Other Intellectual Impairments
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Aphasia
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(Specific) Learning Disabilities (e.g., Spoken language, Written language,
Arithmetic, Reasoning)
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Psychological impairments
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Drug and Alcohol Dependence
The following is a list of assistive technologies that some people with
disabilities use to browse the Web. Assistive technologies are products used
to help people accomplish tasks that they can not accomplish otherwise. For
example, eyeglasses assist those who can not see clearly. When dealing with
computers and the World Wide Web, assistive technologies usually refer to
software adaptations, specially designed hardware devices, and/or standard
devices used in alternative ways which provide user access.
Some assistive technologies rely on the output of other user agents for their
input. User agents include assistive technologies as well as desktop graphical
browsers, text browsers, voice browsers, mobile phones, multimedia players,
plug-ins, and other software to browse the Web.
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Screen reader
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Software, used primarily by users who are blind, that reads the contents
of the screen aloud. Some screen readers use the document tree (i.e., the
parsed document) as their input. However, older screen readers make use of
the rendered version of a document, meaning that document order or structure
may be lost (e.g., when tables are used for layout) and their output may
be confusing.
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Screen magnifier
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Software, used primarily by individuals with low vision, that magnifies a
portion of the screen for easier viewing. Note that at the same time screen
magnifiers make presentations larger, they also reduce the amount that may
be viewed. Screen magnifiers may therefore offer two views of the screen:
one magnified and one default size for navigation.
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ShowSounds and SoundSentry
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Features of some operating systems (e.g., Windows) allow users to receive
visual notification that a warning or error sound has been emitted by the
computer. This feature is important to users who are deaf or hard of hearing.
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Scanning Software
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Software, used primarily by individuals with severe physical or cognitive
disabilities, that highlights (and/or announces) selection choices (e.g.,
menu items, groups of possible phrases, etc.) one at a time. A user selects
a desired item by hitting a switch when the desired item is
highlighted/announced.
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Alternate Keyboards
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Hardware/software devices that provide an alternate way of creating keystrokes
that appear to be coming from the standard keyboard. On-screen keyboards,
speech input, eyegaze keyboards, and sip-and-puff (Morse code) keyboards
are some examples. Alternative keyboards are used primarily by individuals
with disabilities that prevent them from using the standard keyboard (and
usually from using the mouse as well). Programs that can be operated entirely
from the standard keyboard (and don't require the mouse) can be used by
individuals with alternate keyboards.
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Braille and Dynamic Braille
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Braille is a technique involving six dots that are raised in different patterns
to represent letters and numbers so that they may be read by people who are
blind using their fingertips. Grade II braille includes additional codes
that represent common letter groupings (e.g., "th," "ble") to make braille
more compact. An 8-dot version of braille has been developed to allow all
ASCII characters to be represented. Dynamic braille involves the use of a
display where dots can be raised and lowered dynamically to allow any braille
words to be displayed. Only letters and numbers can be represented in braille,
although some braille printers have a utility that allows simple graphics
to be drawn on a sheet using the raised dots at a resolution of approximately
11 dots per inch. Note. The word "braille" should only be
capitalized when referring to Louis Braille, inventor of the system.
About the Web Accessibility Initiative
W3C's Web Accessibility Initiative (WAI) addresses accessibility of the Web
through five complementary activities that:
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Ensure that the technology of the Web supports accessibility
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Develop accessibility guidelines
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Develop tools to facilitate evaluation and repair of Web sites
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Conduct education and outreach
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Conduct research and development
WAI's International Program Office enables partnering of industry, disability
organizations, accessibility research organizations, and governments interested
in creating an accessible Web. WAI sponsors include the US National Science
Foundation and Department of Education's National Institute on Disability
and Rehabilitation Research; the European Commission's DG XIII Telematics
for Disabled and Elderly Programme; IBM, Lotus Development Corporation, and
NCR.
Additional information on WAI is available at
http://www.w3.org/WAI.
Web accessibility guidelines are essential for Web site development and for
Web-related applications development. WAI is coordinating with many organizations
to produce three sets of guidelines:
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"Web Content Accessibility
Guidelines", W. Chisholm, G. Vanderheiden, and I. Jacobs, eds. These
guidelines explain how to design accessible Web content.
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"Authoring Tool Accessibility
Guidelines", J. Treviranus, J. Richards, I. Jacobs, C. McCathieNevile,
eds. These guidelines explain how to build accessible Web authoring tools.
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"User Agent Accessibility
Guidelines", J. Gunderson and I. Jacobs, eds. These guidelines explain
how to design accessible user agents (browsers, multimedia tools, assistive
technologies, etc.)
About the World Wide Web Consortium (W3C)
The W3C was created to lead the Web to its full potential by developing common
protocols that promote its evolution and ensure its interoperability. It
is an international industry consortium jointly run by the MIT Laboratory
for Computer Science (LCS) in the USA, the National Institute for Research
in Computer Science and Control (INRIA) in France and Keio University in
Japan. Services provided by the Consortium include: a repository of information
about the World Wide Web for developers and users; reference code implementations
to embody and promote standards; and various prototype and sample applications
to demonstrate use of new technology. To date, more than 320 organizations
are Members of the Consortium. For more information about the World Wide
Web Consortium, see http://www.w3.org/