10.5.2023
Understand the relationship between principles, guidelines, and success criteria
This study topic was part of the CPACC too, but as we are going deep into WCAG, it's good to make sure the basics are fresh in mind.
Individuals and organisations using WCAG have different needs, so to meet those several layers of guidance are available.
4 principles
These are the foundation of web accessibility:
- Perceivable: Information and user interface components must be presentable to users in ways persons with disabilities can perceive (including blindness, low vision, deafness and hearing loss, limited movement, and cognitive limitations).
- Operable: User interface components and navigation must be operable (functionality from keyboard).
- Understandable: Information and the operation of user interface must be understandable.
- Robust: Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.
13 guidelines
Each principle contains one or more guidelines. The guidelines are not testable, but provide the framework and overall objectives to help authors understand the success criteria and better implement the techniques.
In this list those marked with an asterisk (*) are the ones that are least intuitive for me.
- Perceivable
- Text alternatives
- Time-based media
- Adaptable *
- Distinguishable
- Operable
- Keyboard accessible
- Enough time
- Seizures and physical reactions *
- Navigable
- Input modalities *
- Understandable
- Readable
- Predictable
- Input assistance *
- Robust
- Compatible
Success Criteria
WCAG provides testable success criteria for each guideline. Each success criterion is assigned a level A, AA or AAA. If a site meets the A level criteria, it is said to conform to level A. A site that meets levels A and AA conformst to AA and a site that meets all criteria conforms to level AAA.
Most laws and policies that refer to WGAC 2.1 or 2.0 focus on level AA.
Sufficient and Advisory Techniques
The W3C has published techniques for meeting WCAG success criteria. The techniques are non-normative and can be one of three kinds:
- Sufficient techniques: if the web content meets sufficient techniques, it meets the success criterion.
- Failure techniques: if the web content fails any of these, it fails the success criterion.
- Advisory techniques: optional or conditional techniques may present best practices or possible ways to meet the success criterion.
Is that all?
Note that even if web content conforms to level AAA, it will not be accessible to individuals with all types, degrees, or combinations of disability, particularly in the cognitive language and learning areas.
Metadata may assist users in finding content most suitable for their needs. In conjunction with WCAG, metadata can play a number of roles including:
- Metadata can be used to associate conforming alternate versions of Web pages with Web pages which do not conform, in order to allow users to find the conforming alternate version when they land on a non-conforming page that they cannot use.
- Metadata can be used to locate and also to describe alternate pages where there are multiple versions of a page which have been developed, especially where the alternate pages are optimized for individuals with different disabilities. The user can use the metadata both to locate the alternate versions and to identify characteristics of the versions, so that they can find the one that best meets their needs.
- In addition to being used for whole pages (as in #1 and #2 above), metadata can be used to describe alternate versions of subcomponents of a page. Again, the metadata can be used to find alternate versions of a Web page component as well as to get descriptions of the alternate versions ( if there are several) in order to determine which one would best meet the user's needs.