Understanding the Structure of WCAG 2.0
Since the WCAG 2.0 standard was published by the World Wide Web Consortium (W3C) in December 2008, it has since become the de facto guideline for basing global Web accessibility standards. This is for good reason – WCAG 2.0 substantially improves the end-user experience for people with disabilities. Instead of providing a minimal level of accessibility, WCAG 2.0’s goals were to level the differences between users with and without disabilities as much as possible. The structure of WCAG 2.0 is based on ensuring that four principles are met – content should be perceivable, operable, understandable and robust for all users regardless of disability.
While WCAG 2.0 can appear daunting at first, it can be best explained as a hierarchy comprising of four levels of information.
- Principles. At the highest level, there are four overarching principles that organize WCAG 2.0. These are the principles that Web content should be perceivable, operable, understandable, and robust. For our purposes, these four principles should be seen as providing too high a level of generality.
- Guidelines. Each of the four principles has one or more guidelines associated with them. In total, there are 12 guidelines, each providing a slightly higher level of specificity than their associated principle. For instance, guideline 2.1 requires keyboard access to all functionality. While useful, the guidelines are still quite general and may not provide sufficient specificity for developers trying to meet WCAG 2.0. Instead, the guidelines are best seen as an organizational tool for their associated success criteria.
- Success Criteria. Each of the 12 guidelines has one or more associated “success criteria,” which provide specific expected behavior and functionality from UI elements. In addition, each success criteria has a level of conformance (level A, AA, or AAA). There are a total of 61 success criteria. Focusing at the success criteria level will likely give developers the highest level of return for their efforts.
- Techniques. Each of these success criteria identifies one or more techniques that are required in order to meet or exceed the requirements of the success criteria. WCAG 2.0 provides a plethora of techniques, which are divided into sufficient techniques (generally required to meet a success criteria) and advisory techniques (which further augment meeting a success criteria and which can be considered a best practice). Focusing at the technique level can be a daunting task because each technique can be associated with several different success criteria. Additionally, the techniques are organized by technology and the numbering schema is different from the structure used for organizing principles, guidelines, and success criteria. (A summary of the WCAG 2.0 techniques in available at http://www.w3.org/TR/WCAG20-TECHS/).
To learn more about the benefits of conforming to WCAG 2.0, the global government trend of moving to WCAG 2.0 and information on other accessibility standards like Section 508, download our whitepaper The Global Move to WCAG 2.0 and The Case for Conformance.