Four Principles of Accessibility | Accessibility
Standards Based Development
wcag2.0 guidelines and wcag2.0 Success Criteria are organized around four principles, which lay the necessary foundation that enables any user to access and use web content. Anyone who wants to use the web must have content that is:
1. Perceivable
Perceivable: Information and ui components must be presentable to users in ways they can perceive.
Note: This means that users must be able to perceive the information being presented; the information cannot be invisible to all of their senses.
2. Operable
Operable: ui components and navigation must be operable.
Note: This means that users must be able to operate the interface; the interface cannot require interaction that a user cannot perform.
3. Understandable
Understandable: Information and the operation of the ui must be understandable.
Note: This means that users must be able to understand the information as well as the operation of the ui; the content or operation cannot be beyond their understanding.
4. Robust
Robust: Content must be robust enough so that it can be interpreted reliably by a wide range of user agents, including ats.
Note: This means that users must be able to access the content as technologies advance, or rather, as technologies and user agents evolve, the content should remain accessible.
Note: if any of the four principles of accessibility are not true, users with disabilities will not be able to use the web (at least not to it's and their full extent).
Each principle of accessibility has guidelines and Success Criteria that fall underneath, helping to address the principles for people with disabilities. wcag 2.0 only includes guidelines that address specific problems to people with disabilities; there are quite a few more general usability guidelines that make content more human usable. Problems particular to people with disabilites include issues that block access or interfere with access to the web more severely for people with disabilites.
