Accessible Software Design
Taken from several sources
Users With Disabilities
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Sight
Hearing
Mobility
Cognitive
Language impairment
Seizure disorders
Speech impairments
Why Worry About It?
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Profits
Americans With Disabilities Act
Rehabilitation Act
Legislation elsewhere
It is part of ANSI and ISO standards for
usability
• Moral High Road
Keys to Accessibility
• Minimize barriers
• Provide compatibility with accessibility
utilities
– Screen readers
– Voice input
– Others
Accessibility in the Lifecycle
• Plan early to accommodate
• Include people with disabilities in feedback process
– requirements determination
– usability testing
– Beta testing
• Ensure developers are familiar with accessibility
guidelines
• Ensure test team can recognize accessibility
problems
• Ensure technical support and customer service have
access to accessible environments
How Computers can Become
Accessible
• Features in hardware / OS
• Accessibility Aids
• Specialized applications
• Usability features in applications –
– Allow Customization
– Follow standard conventions
– Use standard controls
Accessibility Aids
• Require cooperation from application
program
• Screen enlargement utilities
• Screen readers
• Voice input utilities
• On screen keyboards
• Keyboard filters
Some Basic Principles
• Flexibility
• Choice of input methods
• Choice of output modalities
• Compatibility with accessibility aids
• Consistency
Keyboard Access is Key
• Blind people cannot maneuver a mouse
• Provide keyboard access to all features
• Fully document keyboard interface
• Model keyboard interface on known interfaces
• Allow users to select text using keyboard
• If possible, provide customizable keyboard shortcuts
• Make sure dialog boxes define the correct tab order
Play Nice for Accessibility Aids
• If, for example, an accessibility aid is going to verbalize
visual info, they need things to be named and labeled
meaningfully
– Ensure that every window, object, and graphic is named
appropriately
– Define correct text labels for all controls
– Give every window a user-friendly caption
– Expose names or descriptions for all images
• Expose your elements to the accessibility software
Color
• Color is an issue for color blind, and visually
impaired
• Use only colors that user can customize – in control
panel
• Use proper foreground / background combinations
• No background images behind text
• Avoid conveying important info via color alone
• Give good contrast of images to background
• Allow MS “High Contrast Option”
Size
• Of importance to visually impaired
• Allow the user to select font and font sizes
for displayed info
• If feasible, provide draft mode, zoom,
and wrap to window features
• Allow the user to adjust size of nondocument elements – such as toolbars
• Make sure application is compatible with
changes to system font
Sound
• Good for visually impaired, bad for hearing
impaired
• Define Sound Schemes
– Allow substitution of visual for sound
– Allow substitution of sound for visual
• Provide a way to turn off sounds
Timings
• Of importance to visually impaired and
cognitively impaired
• Allow user to customize any interface timings
• Allow the user to avoid having messages time
out
• Flashing can cause seizures – allow slowing
down or disabling any rapid screen updates or
flashing
Good Layout is Even More
Important
• Things that help regular users understand what to do
are even more important for visually or cognitively
impaired people
• Text labels immediately to left of or above control
• Not ambiguous which of the above
• Text labels end with : (text not requiring input, no : )
• Icons identified with text below, to right, or in tool tip
• Position related objects near each other
Documentation
• Provide documentation on all accessible features
• Provide documentation in accessible format such as
ASCII text or HTML (or Braille)
• Include descriptions of any illustrations and tables
• Do not convey important information via color or
graphics alone
• Keep high contrast between text and background
• Do not use text smaller than 10 pt
• If possible, bind printed documentation to lie flat
Verifying Accessibility
• Test against guidelines discussed here
• Test compatibility with extra large appearance schemes
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Verify that all features can be used without a mouse
Verify that all keyboard access methods are documented
If MS, test use with accessibility tools/options
Test with commercial accessibility aids
Include people with disabilities and accessibility software
vendors in beta tests
• Distribute free evaluation copies to individuals with disabilities,
disability organizations, and accessibility software vendors
• Include people with disabilities in your usability tests
• Conduct surveys of your users with disabilities
Anything Special About the Web?
• Resources – Web Accessibility Initiative (WAI) –
http://www.w3.org/WAI
• "Web Content Accessibility Guidelines 1.0", G. Vanderheiden,
W. Chisholm, and I. Jacobs, eds., May 1999. W3C
Recommendation: http://www.w3.org/TR/WAI-WEBCONTENT
• “User Agent Accessibility Guidelines", J. Gunderson and I.
Jacobs and E. Hansen, eds., October 2000. W3C Working
Draft: http://www.w3.org/TR/2000/WD-UAAG1020001023
Web Page Accessibility Design
• Provide a “skip to main content” link at the top of each
page
• Structure articles with 2 or 3 levels of headings
• For all images, provide associated text
• For all audio content, include at least one of:
– Caption or pop-up text window
– Textual transcript
– Textual description
• For all video content, include (audio AND text) at least
one of:
– transcript
– description
Web Page Accessibility Design
• For image maps, provide equivalent text menus
• Provide alternative ways to access items contained
within tables
• For online forms that cannot be read by screen
utilities, provide alternative methods of
communication
• Provide an option to display animation in a nonanimated presentation mode
• If accessibility is otherwise impossible, provide a textonly page with equivalent info and functionality
• Follow the standards set by the WWWC for
accessibility of Web content
Visual Disabilities Summary
• Utilities
– Ensure compatibility with screen-reader utilities
– Ensure compatibility with screen-enlargement utilities
• Screen components
– Include meaningful screen and window titles
– Provide associated captions or labels for all controls, objects,
icons, and graphics – including graphical menu choices
– Provide a textual summary for each graphic – including
graphs
– Allow for screen element scalability
– Support system settings for high contrast
– Avoid displaying or hiding info based on movement of cursor
Visual Disabilities Summary
• Keyboard
– Provide a complete keyboard interface
– Provide a logical order of screen navigation
• Color
– Use color as a supplemental or enhancing design
characteristic
– Provide a variety of color selections with a range of
contrast levels
• Create color combinations based on system colors for the
components
• Do not define specific colors
Blindness - WWW Barriers
• images that do not have alt text
• complex images (e.g., graphs or charts) that are not adequately described
• video that is not described in text or audio
• tables that do not make sense when read serially (in a cell-by-cell or
"linearized" mode)
• frames that do not have "NOFRAME" alternatives, or that do not have
meaningful names
• forms that cannot be tabbed through in a logical sequence or that are poorly
labeled
• browsers and authoring tools that lack keyboard support for all commands
• browsers and authoring tools that do not use standard applications
programmer interfaces for the operating system they are based in
• non-standard document formats that may be difficult for their screen reader
to interpret
Low Vision – WWW Barriers
• Web pages with absolute font sizes that do not change
(enlarge or reduce) easily
• Web pages that, because of inconsistent layout, are
difficult to navigate when enlarged, due to loss of
surrounding context
• Web pages, or images on Web pages, that have poor
contrast, and whose contrast cannot be easily changed
through user override of author style sheets
• imaged text that cannot be re-wrapped
• also many of the barriers listed for blindness, above,
depending on the type and extent of visual limitation
Color blindness - WWW
• Color blind online shoppers may not pick up
sale prices – the red doesn’t stand out
• Controlling presentation with style sheets
• User override of author style sheets
Color Blindness – WWW Barriers
• color that is used as a unique marker to
emphasize text on a Web site
• text that inadequately contrasts with
background color or patterns
• browsers that do not support user
override of authors' style sheets
Hearing Disabilities Summary
• Provide captions or transcripts of important
audio content
• Provide an option to display a visual cue for all
audio alerts
• Provide an option to adjust the volume
• Use audio as an enhancing design characteristic
• Provide a spell-check or grammar check utility
Deafness – WWW Barriers
• lack of captions or transcripts of audio on the
Web
• lack of content-related images in pages full of
text, which can slow comprehension for
people whose first language may be a sign
language instead of a written/spoken language
• Any requirements for voice input on Web
sites
Physical Movement Disabilities
Summary
• include weakness, limitations of muscular
control , limitations of sensation, joint
problems, or missing limbs.
• Provide voice-input systems
• Provide a complete and simple keyboard
interface
• Provide a simple mouse interface
• Provide on-screen keyboards
• Provide keyboard filters
Speech or Language
Disabilities Summary
• Provide a spell-check or grammar-check
utility
• Limit the use of time-based interfaces
– Never briefly display critical feedback or
messages and then automatically remove
them
– Provide the user an option to adjust the
length of a time out
Resources - Corporate
• Microsoft
– User Oriented - http://www.microsoft.com/enable/
– Developer Oriented http://msdn.microsoft.com/library/default.asp?url=/
nhp/Default.asp?contentid=28000544
• http://www-3.ibm.com/able/
- links from IBM
Resources - Organizations
• ACM SIGCAPH – Special Interest Group on
Computers and the Physically Handicapped http://www.acm.org/sigcaph/
• www.rit.edu/~easi/access.htm - Equal Access to
Software and Information
• trace.wisc.edu/world/computer_access –
Designing More Usable Computers and
Software
Resources - WWW
• aware.hwg.org/tips - Tips and Techniques for
Accessible Web Authoring
• nadc.ucla.edu/dawpi.htm - Web Access
resource list
Resources - Government
• www.access-board.gov/sec508/508standards.htm
Resources - Evaluation
• www.cast.org/bobby - www site which
will (partially) evaluate a www page for
accessibility
End Accessibility