Components of Web Accessibility

Version: Early Concept Draft 2004.08.27
Note: This document is an unapproved draft and should not be distributed, referenced, or quoted under any circumstances. This document is under development by the Education and Outreach Working Group (EOWG), and will be offered to other W3C groups and the public for review. A change log lists revisions in progress and links to previous versions.

Introduction

The purpose of this document is to briefly show how Web accessibility depends on several components working together. It also shows how improvements in specific components could substantially improve Web accessibility.

How the Components Relate

Whether or not a Web site is accessible to a person using the site ("user") is largely based on:

content - the information on the Web site, including text, images, forms, sounds, etc.
Web browsers, media players, and other "user agents"
in some cases, assistive technology -screen readers, alternative keyboards, switches, scanning software, etc.
Users' knowledge, experiences, and in some cases, adaptive strategies using the Web

The accessibility of the content is largely determined by:

developers' accessibility knowledge, skill, and effort - including designers, coders, authors, etc., which also includes "users" who contribute content and people with disabilities
authoring tools - software that creates Web sites
evaluation tools - Web accessibility evaluation tools, HTML validators, CSS validators, etc.

Guidelines for Components

WAI guidelines work together to inform the different components of Web accessibility:

Web Content Accessibility Guidelines (WCAG) informs content developers, authoring tools, and accessibility evaluation tools.
User Agent Accessibility Guidelines (UAAG) informs Web browsers and media players, including some assistive technologies.
Authoring Tool Accessibility Guidelines (ATAG) informs authoring tools and accessibility evaluation tools.

The basic technologies of the Web are fundamental to Web accessibility:

WCAG, UAAG, ATAG, and W3C technical specifications (HTML, XML, CSS, SVG, SMIL, etc.) are developed in coordination with each other
Web browser, media player, assistive technology, authoring tool, evaluation tool, and content developers all refer to relevant technical specifications

Inter-dependencies Between Components

There are significant inter-dependencies between the components; that is, each component relies on other components for effective accessibility.

[@@ image ? ]

[alt example not revised yet - as recorded in changelog] For example, for alternative text on images:

Technical specification defines ALT (HTML IMG element has ALT attribute)
WCAG, UAAG, and ATAG define how it is implemented for accessibility
Authoring tools allow, encourage, and provide help on ALT
Developers provide the equivalent ALT text
Evaluation tools help check for appropriate ALT
Web browsers, or other user agent, provide human and machine interface to ALT
Assistive technologies provides human interface to ALT in various modalities
Users know how to get the ALT from their browser, or other user agent, and/or assistive technology as needed

When accessibility features are effectively implemented in one component, the other components are more likely to implement them.

When user agents (including Web browser, media player, assistive technologies) support an accessibility feature, users are more likely to demand it and developers are more likely to implement it in their content.
When an accessibility feature is implemented in most sites (content), developers and users are more likely to demand that user agents support it.
When authoring tools make a feature easy to implement, developers are more likely to implement it in their content.
When developers want to implement an accessibility feature, they are more likely to demand that their authoring tool make it easy to implement.

However, if one component does not implement an accessibility feature, there is little motivation for the other components to implement it when it does not result in an accessible user experience.

[@@ image? ]

When one component is weak, sometimes other components can compensate; however, compensation usually involves much more effort and "work arounds" that are not good for accessibility overall. For example,

developers can do more work to compensate for some lack of accessibility support in authoring tools
user agents [@@ tweaks that then break other implementations]

Introduction to Web Accessibility provides additional information about Web Accessibility.

Document Information

Editor: Shawn Lawton Henry. This Web page is is under development by the EOWG.

Last updated $Date: 2004/09/16 02:08:17 $ by $Author: shawn $