Download Accessible Software Design Taken from several sources

Accessible Software Design
Taken from several sources
Users With Disabilities
•
•
•
•
•
•
•
Sight
Hearing
Mobility
Cognitive
Language impairment
Seizure disorders
Speech impairments
Why Worry About It?
•
•
•
•
•
Profits
Americans With Disabilities Act
Rehabilitation Act
Legislation elsewhere
It is part of ANSI and ISO standards for
usability
• Moral High Road
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
• New Features in hardware / OS
• Accessibility Aids
• Specialized applications
• Usability features in applications
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 in accessible format such as
ASCII text or HTML
• 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
•
•
•
•
•
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., 5
May 1999. W3C Recommendation:
http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505
• “User Agent Accessibility Guidelines", J.
Gunderson and I. Jacobs, eds., 28 July 2000.
W3C Working Draft:
http://www.w3.org/TR/2000/WD-UAAG10-
Color blindness
• 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
Motor Disabilities
• include weakness, limitations of muscular control , limitations of
sensation, joint problems, or missing limbs.
• To use the Web, people with motor disabilities affecting the hands or arms
may use
– a specialized mouse;
– a keyboard with a layout of keys that matches their range of hand motion;
– a pointing device such as a head-mouse, head-pointer or mouth-stick; an eyegaze system;
–
•
voice-recognition software;
They may activate commands by typing single keystrokes in sequence
with a head pointer rather than typing simultaneous keystrokes
("chording") to activate commands.
• may need more time when filling out interactive forms on Web sites
Motor Disabilities – WWW Barriers
• time-limited response options on Web
pages
• browsers and authoring tools that do not
support keyboard alternatives for mouse
commands
• forms that cannot be tabbed through in a
logical order (Note: "Tabindex" solution
not yet well supported in browsers.)
Repetitive Stress – Carpal Tunnel
• Voice input allows less use of mouse and
typing
– Problem: WWW sites with streaming audio
conflict with speech recognition
• Alternative keyboard
• Using access keys for shortcuts
• Problem: authoring tool accessibility
Hearing Impairment - Deafness
• To use the Web, many people who are
deaf rely on captions for audio content.
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
Hearing Impaired
• Some WWW pages have audio that is important
part of the content (e.g. university with online
audio lessons)
• Making multimedia accessible
Visual Impairment - Blindness
• To access the Web, many rely on screen readers
–
– outputs this information to a speech synthesizer
and/or
– refreshable braille display.
• Some use text-based browsers such as Lynx, or
voice browsers,
• may use rapid navigation strategies such as
tabbing through the headings or links on Web
pages
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
labelled
• 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
HTML Tables
• Problem: Tables can be hard to read for screen
readers
• you should use the HTML TABLE element and its
supporting elements and attributes (like TR, TD,
TH and CAPTION).
• A simple data table created with proper data table
mark up, might look like this:
Column 1 Header
Column 2 Header
Row 1 Header
Column 1 Row 1
Column 2 Row 1
Row 2 Header
Column 1 Row 2
Column 2 Row 2
HTML Table
• <TABLE border=1>
• <CAPTION>Example of a simple data table created using
HTML markup.</CAPTION>
• <TR><TD></TD><TH>Column 1 header</TH>
• <TH>Column 2 header</TH></TR>
• <TR><TH>Row 1 header</TH>
• <TD>Column 1 Row 1</TD>
• <TD>Column 2 Row 1</TD></TR>
• <TR><TH>Row 2 header</TH>
• <TD>Column 1 Row 2</TD>
• <TD>Column 2 Row 2</TD></TR>
• </TABLE>
HTML for Better Reading
•
HTML 4.0 also allows you to explicitly link header information to columns and
rows using the "headers" attribute of the <TD> and <TH> elements, e.g.:
• Cups of coffee consumed by each senator
Name
Cups
Type of Coffee
Sugar
T Sexton
10
Expresso
No
J. Dinnen
5
Decaf
Yes
•If you use the 'headers' attribute, a browser or screen reader might be
able to expose or read the contents of the cells (if the user wishes) like
this:
•Name: T. Sexton, Cups: 10, Type: Espresso, Sugar: No
Name: J. Dinnen, Cups: 5, Type: Decaf, Sugar: Yes
•because each datum is explicitly associated with its appropriate header.
View the markup code that would
generate this example
•
<TR>
•
<TH id="t1">Name</TH>
•
<TH id="t2">Cups</TH>
•
<TH id="t3" abbr="Type">Type of Coffee</TH>
•
<TH id="t4">Sugar?</TH>
•
</TR>
•
<TR>
•
<TD headers="t1">T. Sexton</TD>
•
<TD headers="t2">10</TD>
•
<TD headers="t3">Espresso</TD>
•
<TD headers="t4">No</TD>
•
</TR>
•
<TR>
•
<TD headers="t1">J. Dinnen</TD>
•
<TD headers="t2">5</TD>
•
<TD headers="t3">Decaf</TD>
•
<TD headers="t4">Yes</TD>
•
</TR>
More Visual Impairment
• Abbreviations in documents make reading them
aloud hard for a mere program
– Expanding abbreviations and acronyms
When in Boston, be sure to visit the
<ACRONYM TITLE="Museum of Fine Arts">MFA</ACRONYM>,
<ACRONYM TITLE="Massachusetts Institute of
Technology">MIT</ACRONYM> and, of course, the
<ACRONYM TITLE="World Wide Web
Consortium">W3C</ACRONYM>. These destinations are
easily reached via
<ABBR TITLE="Massachusetts Avenue">Mass. Ave.</ABBR>
or <ABBR TITLE="Memorial Drive">Mem. Dr.</ABBR>.
More Visual Impairment
• The WWW is full of visual info, graphics,
multimedia
Visual Impairment – Low Vision
• There are many types of low vision
• To use the Web, some people use extra-large
monitors, and
• increase the size of system fonts and images.
• Others use screen magnifiers
• Some use bright contrast
• or choose typefaces is legible given their condition
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
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/swreferences.html
- 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