Components of Web Accessibility

Version: Early Concept Draft 2004.08.11
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.

This document explains components of Web accessibility. Introduction to Web Accessibility provides additional information about Web Accessibility.

Overview

In order for the Web to be accessible, several components must work together, as explained below.

The User Experience

A person using a Web site ("user") brings their own knowledge, experiences, and in some cases adaptive strategies. For example, users have varying levels of knowledge of hoe to use computers and Web browsers, and have different experiences with different Web sites. Some people with disabilities use adaptive strategies, that is, they interact with Web sites in a particular way to meet their needs.

User Interaction

Whether or not a Web site is accessible to a user is largely based on:

• content (the information on the Web site, including text, images, forms, sounds, etc.)
• user agent(including Web browsers, media players, etc.)
• assistive technology (screen readers, alternative keyboards, switched, scanning software, etc.), in some cases

Content Development

The accessibility of the content is largely determined by:

• developers'(including designers, coders, etc.) accessibility knowledge, skill, and effort
• authoring tools (software that creates Web sites) support for accessibility
• evaluation tools (Web accessibility, HTML validators, CSS validators, etc.) for accessibility and markup validation

Guidelines

WAI guidelines and W3C technical specifications (HTML, XML, CSS, SVG, SMIL, etc.) work together to inform accessible Web content and tool development.

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

Inter-dependencies

There are significant inter-dependencies between the components; that is, each component relies on other components to form an effective system.

For example, for alternative text on images:

• Technical specification defines ALT (HTML IMG element has ALT attribute)
• WCAG, ATAG, and UAAG 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
• User agents 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 user agent and/or assistive technology as needed

When one component is weak

When any one component does not work effectively, it complicates the system and results in poorer accessibility. In some cases, the other components can compensate some; however, that usually involves much more effort and "work arounds" which are not good for accessibility in the big picture.

Currently the burden of developing accessible content is heavy on developers and thus requires a high level of developer knowledge, skill, and effort. Better authoring toolscould lower the burden on developers, and increase the accessibility of content.

Getting implementation in the cycle

One of the reasons that some accessibility features are not effectively implemented throughout the system is that there is little motivation for one component to implement a feature when it is not implemented well in the other components.

With authoring tool and user agent implementation:

• user agents are less likely to implement accessibility features that most sites don't use, because there is little demand for it
• authoring tools are less likely to implement accessibility features that developers aren't demanding
• developers are less likely to implement accessibility features that are not supported by common user agents or that are difficult to do with their authoring tool

If common user agents better supported a given accessibility feature, developers would be more inclined to want to implement it and demand that their authoring tool make it easy to implement.

Document Information

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

Last updated $Date: 2004/08/12 20:40:14 $ by $Author: shawn $