Michael Gaigg: Über UI/UX Design

Web Content Accessiblity Guidelines (WCAG) 2.0: Overview and Structure

Posted by Michael Gaigg

Overview

Last week the W3C announced the publishing of the Web Content Accessibility Guidelines (WCAG) 2.0 as a final Web Standard "W3C Recommendation". This is good news for many reasons:

• Guidelines are more specific, e.g. specifying contrast ratio or time-based actions in seconds.
• Success Criteria are written in a technology neutral fashion.
• Success Criteria are written as testable statements.
• Past killer arguments like "Javascript is forbidden" are now included as a technique to enhance accessiblity.
• Gathering 'implementation experience' is now part of the W3C Process.
• Guidelines include requirements related to informing users of data entry errors.

WCAG 2.0 Overview showing Principles, Guidelines, and Success Criteria (Level A, Level AA, Level AAA).

But what I personally like the best is the revamped structure called layers of guidance:

Structure

The four principles of Web accessibility: perceivable, operable, understandable, and robust.

The WCAG 2.0 define a logical hierarchy of accessibility guidelines called layers of guidance. All of these layers work together to provide guidance on how to make content more accessible.

Principles

The foundation is built on four principles that are essential for anyone to access and use Web content, i.e. every Web content must be:

1. Perceivable
2. Operable
3. Understandable
4. Robust

These principles are the four pillars of Web accessibility and describe at a high level what can be done to assist users with varying needs to successfully access your content.

Guidelines

The 12 WCAG 2.0 Guidelines provide basic goals for creating accessible content.

The 12 guidelines are basic goals that authors of Web content should work toward in order to create accessible content. None of them are testable and are only meant as a framework of overall objectives. The guidelines are:

• 1.1 Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
• 1.2 Provide alternatives for time-based media.
• 1.3 Create content that can be presented in different ways (for example simpler layout) without losing information or structure.
• 1.4 Make it easier for users to see and hear content including separating foreground from background.
• 2.1 Make all functionality available from a keyboard.
• 2.2 Provide users enough time to read and use content.
• 2.3 Do not design content in a way that is known to cause seizures.
• 2.4 Provide ways to help users navigate, find content, and determine where they are.
• 3.1 Make text content readable and understandable.
• 3.2 Make Web pages appear and operate in predictable ways.
• 3.3 Help users avoid and correct mistakes.
• 4.1 Maximize compatibility with current and future user agents, including assistive technologies.

Success Criteria

WCAG 2.0 Success criteria shown in three column: column 1 (red) are Level A, column 2 (yellow) are Level AA, column 3 (green) are Level AAA.

Now, the success criteria is where the meat is. For each Guideline, testable success criteria are provided. Every Web content or series of Web content (complete web page or series of connected pages) can be tested and evaluated against these criteria and further assigned a true/false (equals pass or fail) value.
These success criteria are further divided into three levels of conformance, meaning satisfying all the requirements of a given standard, guideline or specification:

• Level A (lowest; minimum level of conformance)
• Level AA
• Level AAA (highest)

The notion of conformance is so important that I will discuss it in a separate blog entry.

Sufficient and Advisory Techniques

Up until now all the principles, guidelines, and success criteria are written in a technology neutral fashion. That's great but what now? The Working Group has identified and published examples for HTML implementations that should serve as examples and tutorials and are kept in the living document called Techniques for WCAG 2.0. This document explains a variety of techniques on how to implement the given guideline for each success criteria. The list is not complete and will be expanded as new techniques are discovered.

The techniques fall into two categories:

• Sufficient techniques: considered to be sufficient to meet a success criteria.
• Advisory techniques: enhance accessibility, but did not qualify as sufficient techniques.

Most Success Criteria have multiple sufficient techniques listed. Any of the listed sufficient techniques can be used to meet the Success Criterion. Also there may be other techniques which are not documented by the working group that could also meet the Success Criterion. This is especially true for content that is not HTML.

Resume & Criticism

I'm really excited about the WCAG 2.0, their clear structure and promising, almost marketing-like wording. I also like the amount of effort taken to document examples, techniques and common failures.
What I miss is the programmer perspective that outlines each element with its associated success criteria and code samples, e.g. how can I make tables accessible, what about links, captcha, maps, etc.? I think this work is up to us and I will continue to tackle this issue by grouping, summarizing and compiling elements so I can publish them on this blog.

What are your opinions on WCAG 2.0?