WCAG Extensions Framework

WCAG 2.0 Extension Requirements

Abstract

This document outlines the requirements that the Web Content Accessibility Guidelines Working Group (WCAG WG) has set for the development of Web Content Accessibility Guidelines (WCAG) 2.0 extensions. These extension requirements build on the existing requirements for WCAG 2.0, and are designed to work in harmony with the WCAG 2.0 standard.

Introduction

Web Content Accessibility Guidelines 2.0 (WCAG 2.0) explains how to make Web content accessible to people with disabilities. Since the release of WCAG 2.0 in December 2008 WCAG 2.0 has been widely adopted and implemented. As a result of both feedback from implementers and significant changes in technologies, the WCAG WG is pursuing the development of Extension specifications and support materials to address special topic areas as needed, including (but not limited to) mobile devices, cognitive impairments and learning disabilities, and low vision.

The underlying goal of each Extension is the same as for WCAG 2.0 – to promote accessibility of Web content. Each Extension also needs to meet additional goals addressed in this document including:

1. Satisfy pre-existing requirements for WCAG 2.0
2. Ensure that web pages which conform to WCAG 2.0 plus an extension also conform to WCAG 2.0 on its own
3. Ensure that all WCAG extensions are compatible with each other
4. Define a clear conformance model for WCAG 2.0 plus extensions
5. Ensure the conformance structure utilizes the WCAG 2.0 A/AA/AAA model

Satisfy pre-existing requirements for WCAG 2.0

The WCAG 2.0 Requirements document (http://www.w3.org/TR/wcag2-req/) provides details used during the development of WCAG 2.0, including key goals related to technology independence, clearly defined conformance requirements, and more which are still relevant and important. As with WCAG 2.0 the WCAG Extensions will provide techniques and supporting documentation to assist in implementation efforts, and any criteria modified or introduced by extensions will need to be verifiable by implementers.

Ensure that web pages which conform to WCAG 2.0 with an extension also conform to WCAG 2.0 on its own

Extension specifications are expected to offer modifications to existing WCAG 2.0 success criteria as well as offer additional guidelines and success criteria but Extensions may not weaken what is required of web content.

For example:

• An existing success criteria may change in priority from a lower level to a higher level, but not the other way around. For example, a Level A Success Criteria cannot move to Level AA.
• A new success criteria may be added
• Existing success criteria may be modified but the resulting change must still satisfy WCAG 2.0 success criteria

Strive to make all WCAG extensions compatible with each other

Extensions will ideally co-exist to allow authors to implement multiple extensions. Group members working on different extensions should maintain good communication about extension work in progress with the Working Group and with other Task Forces writing extensions to minimize conflicts wherever possible.

Note for release: Please consider the requirement to make extensions compatible with each other carefully. The Working Group is concerned about whether it is possible to require full compatibility and is also concerned about the difficulty of incorporating requirements for conflicting extensions into a future guidelines update. Feedback from reviewers on this point is specifically requested.

Define a clear conformance model for WCAG 2.0 plus extensions

The WCAG 2.0 Requirements document provides details about conformance that needs to be met for Extensions, but Extensions also need to provide conformance details that indicate the relationship of Extension conformance and WCAG 2.0 conformance. Extensions must specify that conformance claims indicate that a page conforms to WCAG 2.0 as a base and to the extension as an additional layer of conformance.

Ensure the conformance structure utilizes the WCAG 2.0 A/AA/AAA model

New wording, based on 11/2/15 call conversation):

Extensions will utilize the WCAG 2.0 A/AA/AAA structure. Extensions will define additional or changed success criteria and will specify at what Level those criteria are provided. When a page conforms to an Extension at a specific level, that page must conform to WCAG 2.0 at the same level.

(old thoughts below)

[Determination of the WCAG 2.0 Extension conformance structure is a topic that needs more discussion] Options:

1. Should Extensions have A/AA/AAA levels or be level-less?
   1. If we have levels that is getting closer to “WCAG 2.1” territory and will likely increase development time for the extension.
2. If Extensions have A/AA/AAA, can a WCAG 2.0 A page conform to WCAG 2.0 Extension "X" at a AA level? Or should Extension level parallels WCAG 2.0 claim? e.g. A WCAG 2.0 A conformant page can conform to Extension level A but not AA. A AA page can conform to the Extension level AA.
3. Should Extensions assume a WCAG 2.0 AA conforming base, meaning that a WCAG 2.0 A page would need to reach AA before applying an extension?
   1. One consequence of this is that level changes for a SC is of no consequence except AAA to AA.