Transcript Document

Understanding
Universal Web
Accessibility
Bebo White
SLAC
[email protected]
27 Sept 2002
What Does Accessibility
Mean?
"The power of the Web is in its
universality. Access by everyone
regardless of disability is an
essential aspect.“
-- Tim Berners-Lee
W3C Director
Inventor of the World Wide Web
Who Are the Disabled?
• An estimated 20% of Americans have
some form of disability (Microsoft Web
site)
• Global statistics are probably similar
• Not just the obvious
– Blind, deaf, severe motor disabilities
• But more commonly
– Color deficiency, reading disorders, aging
The ADA and Section 508
• In 1998, the U.S. Congress amended the
Rehabilitation Act to require Federal
agencies to make their electronic and
information technology accessible to
people with disabilities
• Inaccessible technology interferes with
an individual's ability to obtain and use
information quickly and easily
• Disabled employees must have access to
information comparable to others
The ADA and Section 508
(cont)
• Section 508 was enacted
– to eliminate barriers in information
technology
– to make available new opportunities for
people with disabilities
– to encourage development of technologies
that will help achieve these goals
• Applies to, but is not limited to,
computers, ancillary equipment,
software, telecommunication products,
information kiosks, Web sites,
multimedia, and office equipment
Web Content Accessibility
Guidelines (WCAG)
• Published by the W3C
• Now at Version 1.0
• http://www.w3.org/TR/WAIWEBCONTENT
General WCAG 1.0
Principles
• Provide a text equivalent for every nontext element (e.g., via "alt", "longdesc",
or in element content).
• Ensure that all information conveyed
with color is also available without color,
for example from context or markup.
• Clearly identify changes in the natural
language of a document's text and any
text equivalents (e.g., captions).
General WCAG 1.0
Principles
•
Organize documents so they may be
read without style sheets.
• Ensure that equivalents for dynamic
content are updated when the dynamic
content changes.
• Until user agents allow users to control
flickering, avoid causing the screen to
flicker.
• Use the clearest and simplest language
appropriate for a site's content.
Accessibility Tools
• Bobby http://bobby.watchfire.com/bobby/ht
ml/en/index.jsp
• http://www.w3.org/WAI/ER/
existingtools.html
Bobby and the HKU Site
Universal Accessibility
“Anyone or anything using any kind
of Web client technology on any
Web-enabled platform should be
able to visit any site and get a full
and complete understanding of the
information contained therein as
well as have the full and complete
ability to interact with that site as
necessary”
Web
Server
Internet
Benefits of Universal
Accessibility
• Increase market share and audience
reach
– Improve usability for non-disabled and
disabled visitors
– Support for low literacy levels
– Improve search engine listings and resource
discovery
– Support for the Semantic Web
– Repurpose content for multiple formats or
devices
– Increase support for internationalization
– Assisting access for low-bandwidth users
Benefits of Universal
Accessibility (2)
• Improve efficiency
– Reduce site maintenance
– Site search engine improvements
– Repurposing content
– Address server-load
– Address server-bandwidth
• Demonstrate social responsibility
• Reduce legal liability
Market Share Benefits of
Accessible Web Site
Design
Usability
Checkpoints
Clear
Navigation
Public Repurpose Internationalization
Low
Support
Search
Bandwidth
low
Engines
literacy
YES
YES
Device
independence
YES
Clear Content
YES
YES
Text
Alternatives
YES
YES
Metadata
YES
Separate
Structure from
Presentation
YES
Captioning for
Multimedia
YES
Color
Independence
YES
Table Attributes
W3C
Technologies
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
(from Andrew Arch and Chuck LeTourneau)
Technical Efficiency
Benefits of Accessible Web
Site Design
Checkpoints
Site
Search
Engine
Repurpose
YES
Clear Navigation
Device
independence
YES
Clear Content
YES
Text Alternatives
YES
Metadata
YES
Separate Structure
from Presentation
YES
Captioning for
multimedia
YES
Color
Independence
W3C technologies
Server
Maintenance Server
Bandwidth
load
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
(from Andrew Arch and Chuck LeTourneau)
The Key to Universal
Accessibility is
Repurposing
•
•
•
•
•
Content is what you say
Presentation is how you present it
Content is invariant
Presentation is variable
Repurposing is matching content to
presentation
• Tools for repurposing are available
now
Content
Complex
System
Presentation
(e.g.,
Interface
1
User
1
Interface
2
User
2
Interface
3
User
3
RDF)
Meta-layer
of all
communication
between user
and system
Use Profiles
(e.g.,
CSS,
XSL,
XHTML,
XML)
Interface Generator
“Accessible design is not
only good design, it’s good
sense!”