WCAG Overview:
The first thing to understand is that WCAG is not a simple list of technical things to do or not do on your website, but rather a list of objectives your website must achieve.
There are twelve Guidelines, arranged under four Principles. The Guidelines “provide the basic goals that authors should work toward in order to make content more accessible to users with different disabilities”.
Each of the Guidelines is provided with testable Success Criteria, allowing testing to three levels of conformance (A, AA and AAA).
The techniques which should be used to achieve conformity are not exactly mandated in the standard (any which satisfy the criteria are in principle acceptable). Nevertheless the ancillary documentation provides lists of techniques of two types.
Sufficient Techniques are those which, if used, will be sufficient for meeting the Success Criteria. In most cases there are multiple alternatives, and indeed it is intended that this list will be updated over time as technology changes. In practice the use of these seems almost mandatory to achieve conformance without the extra hurdle of getting an unlisted technique accepted.
Advisory Techniques go beyond the Success Criteria, to better meet the guidelines.
It is these Principles, Guidelines, and Success Criteria which make up the standard, supported by the future-extendable List of Techniques which are provided to assist in meeting the standard.
In order to give you a firm grasp of what WCAG compliance actually involves, there follows our list all the twelve Guidelines as clickable links, supplemented by a detailed dissection of an example Criterion, Technique and Test. This shows how in practice it is the Sufficient Techniques which are at the heart of actual testing, rather than having test procedures directly defined in the Criteria specifications, as one might have expected from reading the higher-level documentation.
List of Guidelines
Guidelines for Principle 1 - Perceivable
- 1.1 Text Alternatives: Any non-text content should be provided with text alternatives , allowing change into other needed forms of presentation
- 1.2 Time-based Media: Alternatives should be provided for time-based media such as audio and video.
- 1.3 Adaptable: Content should be presentable in different ways (eg simpler layout ) whilst preserving information or structure.
- 1.4 Distinguishable: It should be easier for users to hear and see content, including separating foreground and background.
Guidelines for Principle 2 - Operable
- 2.1 Keyboard Accessible: All functionality should be available from a keyboard.
- 2.2 Enough Time: Users should be given sufficient time to read and use the content.
- 2.3 Seizures: Content should not be designed in a way that is known to cause seizures.
- 2.4 Navigable: Ways should be provided to help users to navigate, to find content and to determine where they are.
Guidelines for Principle 3 - Understandable
- 3.1 Readable: Text content should be readable and understandable.
- 3.2 Predictable: Web pages should appear and operate in ways the user can predict.
- 3.3 Input Assistance: Users should be helped to avoid and correct mistakes.
Guidelines for Principle 4 - Robust
How are the Success Criteria Defined ?
To examine the nature of the Success Criteria, let us choose as an example to examine Guideline 1.3 - Adaptable.
There are three Success Criteria, the first of which is 1.3.1 - Info and Relationships. This is a Level A criterion (necessary for even the lowest level of conformity).
It is defined as:
1.3.1 Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text.
This brief sentence is fleshed out by eight paragraphs headed “Intent of this Success Criterion”, the flavour of which can be seen from the following quotes:
“The intent of this Success Criterion is to ensure that information and relationships that are implied by visual or auditory formatting are preserved when the presentation format changes…..Sighted users perceive structure through various visual cues — headings are often in a larger, bold font….When such relationships are perceivable to one set of users, those relationships can be made to be perceivable to all. One method of determining whether or not information has been properly provided to all users is to access the information serially in different modalities….An on-line catalog may indicate prices using a larger font colored red. A screen reader or person who cannot perceive red, still has the information about the price as long as it is preceded by the currency symbol.”
Three benefits are then described, followed by five examples of success, including
“A bus schedule consists of a table with the bus stops listed vertically in the first column and the different buses listed horizontally across the first row. Each cell contains the time when the bus will be at that bus stop. The bus stop and bus cells are identified as headers for their corresponding row or column so that assistive technology can programmatically determine which bus and which bus stop are associated with the time in each cell.”
There follows information on multiple “Sufficient Techniques”, listed as applicable in certain specified situations.
One of these Techniques (which is also Sufficient for two other different Criteria) is
G140: “Separating information and structure from presentation to enable different presentations”
which is described thus:
“The objective of this technique is to facilitate the interaction of assistive technology with content by logically separating the content’s structural encoding from the presentational encoding. Structural encoding is the indication of elements such as headings, paragraphs, lists, tables, etc. ….”
The objective is to
“encode the structure unambiguously enough for assistive technology to interact with the page effectively”.
Two examples of G140 are given, one of which is “HTML with CSS”, described thus:
“CSS is used to format the document based on its structural properties…. Assistive technologies can substitute or extend the CSS to modify presentation, or ignore the CSS and interact directly with the structural encoding.”
Finally a Test is specified, apparently to determine if the Technique is being applied. We quote it in full:
Procedure
1 Examine the encoding of a document.
2 Check that structural information and functionality are explicitly provided and is logically separated from presentational information.
Note that this test is associated with the Sufficient Technique G140, rather than directly with the Criterion 1.3.1. Thus we see that, in this case at least, actual conformance testing is on the basis of checking the use and proper implementation of one of the specified techniques. Establishing conformance via a non-listed technique, though in principal it seems allowable, would clearly be difficult in practice.
Accessing the WCAG Documentation
The principal source page to access the latest copies of all WCAG documentation is the Web Accessibility Initiative page on the World Wide Web Consortium (W3C) website.
A extensive variety of cross-linked support documents is available on the website, in addition to the actual official WCAG 2.0 standard itself. The contents and relationships between these various documents are shown in a diagram on the page “The WCAG 2.0 Documents”.
The best way to examine the detail is to look at the page How to Meet WCAG 2.0, which lists and links it all.
Use the links below or on the right to explore further.
