Components of Web Accessibility

Version: Early Concept Draft 2004.08.16
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.)
• user agent (including Web browsers, media players, etc.)
• assistive technology (screen readers, alternative keyboards, switched, scanning software, etc.), in some cases

Users' knowledge, experiences, and in some cases, adaptive strategies using the Web have a role in an accessible user experience. (Users can also be developers.)

The accessibility of the content is largely determined by:

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

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

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

• WCAG, ATAG, UAAG, and W3C technical specifications (HTML, XML, CSS, SVG, SMIL, etc.) are developed in coordination with each other
• Authoring tool, evaluation tool, user agent, assistive technology, 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.

[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, 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 results in poorer accessibility. In some cases, the other components can compensate some; however, compensation usually involves much more effort and "work arounds" that are not good for accessibility overall.

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

Getting implementation in the cycle

When accessibility features are effectively implemented in one component, the other components are more likely to implement them. However, there is little motivation for one component to implement a feature when it is not implemented in the other components.

With authoring tool and user agent (including assistive technologies) implementation:

• user agents are less likely to implement accessibility features that most sites do not use (in their content), because there is little demand for it
• authoring tools are less likely to implement accessibility features that developers are not 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 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.

Related Pages

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: 2004/08/28 02:57:35 $ by $Author: shawn $