Transcript accessibility

Accessibility – 1h
Why produce web sites for people
with a disability?
• Moral Reasons
• Business
– A growing market that gets bigger as the population ages
– Loyal customer base
• The wider view
– Accessible sites benefit almost everyone (Universal Design Concept)
• Legislation
– Disability Discrimination Act (1995)
– Special Education Needs and Disability Act (2001)
– Section 508 (USA)
Inclusive Design
• Accessibility
– Physical access to equipment (devices, times, places)
– Everyone has impairments at different times, in different contexts.
“Temporarily unimpaired”
– “Disability” and “handicap” are the result of society’s failure to cope
• Usability
– The quality of the interaction (flexibility, learnability, user satisfaction,
errors, speed)
• Acceptability
– The acceptability of the system to users in its context of use
Incidence of Impairments in the EU
Reduced co-ordination
Reduced strength
Cannot use one arm
Cannot use fingers
Intellectually impaired
Dyslexic
Language impaired
1
Speech impaired
Low vision
Blind
Hard of hearing
Profoundly deaf
Walks with aid
Wheelchair user
0
5
10
15
20
25
30
35
40
45
50
Figures in millions
55
60
65
(Gill, 1997)
70
75
80
85
Disability/Impairment facts:
• UK - 8.5 million people
(UK Office of National Statistics)
• UK Disability Discrimination Act (1995)
– A person is considered disabled if they have …a physical or mental
impairment which has a substantial and long term adverse effect on
their ability to carry out normal day-to-day activities
– Disabled people have the right of access to the same services as the
rest of us
– “Reasonable adjustment” is required to accommodate disabled users
– Latest Code of Practice refers to Web Accessibility
A financial reason...
Charge:
In 2000 the Sydney Organising Committee for the Olympic
Games (SOCOG) was sued for having an inaccessible web site
by a visually-impaired user who was unable to access
ticketing information, event schedules or postings of event
results.
Verdict:
The court determined that the complaint was correct and
SOCOG was found guilty of breaching the Disability
Discrimination Act and fined.
Accessibility - Disability
• Impairment of sight, hearing or movement
• Difficulty in processing certain types of
information
• Difficulty in reading or understanding text
• Unable to use certain input devices (e.g.
mouse, keyboard)
• May not understand/speak fluently the
language in which the document is written
Accessibility - Context
• Text-only screen, small screen, slow internet
connection
• Early version of a browser, a different browser
entirely (e.g. Lynx), a voice browser (e.g.
Home Page Reader, Jaws), or a different
operating system
• Users may be in a situation where their eyes,
ears or hands are busy or interfered with (e.g.
working in a busy, loud environment)
Assistive Technologies for physical
disabilities - examples
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Drag-lock
Keyboard customisation
Simple switches
Head movement
Foot controlled devices
Joysticks
Touch pads
Trackballs
Light pens
Assistive technologies for other
disabilities - examples
Visual impairment
Screen readers
Redirect monitor output to
speech synthesis or a
refreshable Braille display
Audio browsers
Read and interpret HTML
(and style sheets) and are
capable of producing inflected
speech output
Voice recognition
• Hearing impairment
– Induction loops
– System sounds &
Symbols (e.g. Sound
Sentry)
• Others
– Speech synthesisers
– Word- / phraseprediction
Accessibility Evaluation Tools
• But note that compliance with automated
checking does not necessarily make sites
accessible (see Diaper & Worman, 2003)
• There is no single tool that can be used to
guarantee absolute accessibility
• Human evaluation is still required
• Guidelines are available
– http://www.w3.org/WAI/
Conformance Levels
• Priority 1: Checkpoints that must be satisfied
otherwise one or more groups will find it impossible to
access information in the web site.
• Priority 2: Checkpoints that should be satisfied
otherwise one or more groups will find it difficult to
access information in the web site.
• Priority 3: Checkpoints that may be addressed
otherwise one or more groups will find it difficult to
access information in the web site.
Web Content Accessibility Guidelines
• HTML tags (elements)
<element_name attribute=“value”>
• Cascading Style Sheets
– For controlling presentation (e.g. for controlling the font and
colour attributes of a particular tag)
– Allows the actual html file to contain “meaning”
• Non-HTML technologies generally pose greater problems
than HTML
Provide equivalent alternatives to auditory
and visual content
• Text equivalents of non-text content
– Includes: images, animations, applets, buttons,
sounds, frames, audio and video files
– “alt” “longdesc” attributes, element content
– Text can be output to speech synthesizers, voice
browsers and braille displays
– Helps blind, deaf and learning impaired
Examples: An image of the moon
• As an image
<img src=“moon.jpg” width=“100” height=“100”
alt=“Photo of the Moon”>
• As an image/link to further information (inside an anchor
element <a>….< /a>)
<img src= ………… alt=“Go to Moon Information Page”>
• As a purely decorative image – no relevance to content
<img src=“moon.jpg” width=“100” height=“100”
alt=“”>
• “longdesc” attribute could also be used
What can you see in
these images?
Don’t rely on colour alone
• Text and graphics must be understandable
when viewed without colour
• Helps users with a visual impairment
– Colour blindness (8% males, 0.5%females)
– Inability to distinguish colours due to insufficient
contrast
• Quick test: print out web pages in black &
white
Use mark-up and style sheets and do so
properly
• Use header elements to describe the document’s information structure
and not to control presentation (e.g. changing font type, size or colour):
– <h1> major heading
– <h2> sub heading
– <h3> sub, sub heading etc.
• Use tables for tabular information not presentation
• Use markup rather than images to give information
• HTML has specific elements for describing:
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Lists <ol>, <ul>, <dl>
Quotes <q>, <blockquote>
Abbreviations <abbr>
Acronyms <acronym>
Use mark-up and style sheets...
• Control presentation with style sheets
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Format text
Control layout
Browsers will process html associated with meaning
Pages controlled using attached style sheets will
download faster
• Use relative (e.g. %) rather than absolute units in
markup language html attribute values and style
sheet property values
Design for device independence
• Allow users to interact with the web site using their preferred
input (or output) device e.g. mouse, keyboard, head wand,
track ball etc.
• Text equivalents for images make it possible for users to
interact with them without a pointing device
• Usually, web pages that allow interaction through the
keyboard are also accessible through speech input or a
command line interface
Design web pages for keyboard interaction
• Produce a logical tab order through links, form controls and
objects
– use the “tabindex” attribute which can be placed in: anchor, area,
object, button, input, select and textarea elements
– tabindex values can be any positive integer including zero (lowest
priority in the tab sequence)
Example using anchors:
<a href=“chapter1.htm” tabindex=“1”> Chapter
1 </a>
<a href=“chapter2.htm” tabindex=“2”> Chapter
2 </a>
Provide clear navigation mechanisms
• Clearly identify the target of each link
– Link text should be concise, and meaningful enough to
make sense when read out of context e.g try to avoid
writing “click here”
– The target of a link can be further clarified using the “title”
attribute (general purpose)
• Provide a site map
• Provide navigation bars
• Group related links
Summary (1/2)
• Using HTML to convey meaning/structure rather
than for presentation (use style sheets)
• Use technologies compatible with assistive
technologies (screen readers, speech browsers,
screen magnifiers, alt input devices)
• Be aware of improved accessibility features in
“embedded interfaces” (e.g. Flash MX 2004) and
monitor others for improvements (pdf, javascript).
Watch for accessibility features being limited to fullprice products eg Adobe Acrobat
Summary (2/2)
• Take advantage of accessibility solutions for
technologies (Dreamweaver accessibility stylesheets,
Java accessibility API)
• Use accessibility evaluation tools
• Test with various browsers
• Follow the web content accessibility guidelines
(WCAG 1.0) produced by the W3C, and track new
developments (WCAG 2.0)