Understanding the Four Principles of Accessibility
The principles of accessibility success criteria are the testable statements that define how Web content meets (conforms to) WCAG 2.0.
Principles of Accessibility:
- Perceivable - Information and user interface components must be presentable to users in ways they can perceive. This means that users must be able to perceive the information being presented (it can't be invisible to all of their senses)
- Operable - User interface components and navigation must be operable. This means that users must be able to operate the interface (the interface cannot require interaction that a user cannot perform)
- Understandable - Information and the operation of user interface must be understandable. This means that users must be able to understand the information as well as the operation of the user interface (the content or operation cannot be beyond their understanding)
- Robust - Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies. This means that users must be able to access the content as technologies advance (as technologies and user agents evolve, the content should remain accessible)
Each of the success criteria listed above, is identified with one of three priority levels.
- Level A establishes a baseline level of conformance, and covers a basic set of core accessibility issues (such as alternate text on images and captions and videos).
- * Level AA includes additional success criteria such as providing a visible focus indicator for keyboard users, and ensuring sufficient color contrast.
- Level AAA is the highest level of conformance. Conforming to WCAG 2.0 at Level AAA would mean all 63 success criteria have been met.
* The University of Wisconsin Parkside's target for meeting information technology accessibility standards is WCAG 2.0 Level AA.The Level AA success criteria provide a reasonable goal for websites / web applications, LMS / course content, and also function as a helpful metric for services that are not specifically web-based.