Requirements for WCAG 2.0 Checklists, Techniques, and Test Files

W3C Working Draft 25 January 2005

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Latest version:
Michael Cooper, Watchfire


This is a W3C Working Draft produced by the Web Content Accessibility Guidelines Working Group (WCAG WG). It describes requirements for Checklists and Techniques described by the Web Content Accessibility Guidelines 2.0 (WCAG 2.0). These requirements are related to but different from Requirements for WCAG 2.0 in that "Requirements for WCAG 2.0 Checklists, Techniques, and Test Files" specifies requirements for the technology-specific documents produced by the WCAG WG while "Requirements for WCAG 2.0" specifies general requirements for the general usability of documents produced by the WCAG WG. The Working Group encourages feedback about these requirements as well as participation in the development of WCAG 2.0 by people who have experience creating Web content that conforms to Web Content Accessibility Guidelines 1.0.

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C.

Send comments about this document to the Web Content Accessibility Guidelines Working Group mailing list. The archives for this list are publicly available.

This document was produced under the 5 February 2004 W3C Patent Policy. The Working Group maintains a public list of patent disclosures relevant to this document; that page also includes instructions for disclosing [and excluding] a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) with respect to this specification should disclose the information in accordance with section 6 of the W3C Patent Policy.

This document has been produced as part of the W3C Web Accessibility Initiative (WAI). The goals of the WCAG WG are discussed in the Working Group charter. The WCAG WG is part of the WAI Technical Activity.

This document describes requirements for creating Checklists and Techniques for the Web Content Accessibility Guidelines 2.0. It is a draft document that does not fully represent the consensus of the group at this time. Consensus is expected to be achieved shortly and work on creating the Techniques documents to proceed.

This is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR/.

1. Introduction

The Web Content Accessibility Guidelines 2.0 creates a technology-independent set of Web accessibility guidelines by providing a set of high-level guidelines, and providing technology-specific information in auxiliary documents that are more frequently updated and may be non-normative. This document sets forth requirements for providing those documents, as summarized in Priorities and Techniques. Specifically, this set of requirements fulfills WCAG 2.0 Requirements to provide technology-specific Checklists and technology-specific Application Information.

This document describes requirements both for the source files used to store techniques and for the documents that will be generated from the source files. The source files will likely only be viewed for editing purposes and will exist in the best format and organization that fulfills the requirements (i.e., they are not likely to be available in HTML for general use). From these sources files we intend to generate a variety of views (see Appendix 1 Output Formats ). Each view may have its own requirements. The three views currently under discussion are comprehensive Techniques ( 4. Techniques Requirements ), Checklists ( 5. Checklist Requirements ), and Test Files ( 6. Test File Requirements ).

Other W3C groups have expressed interest in using the schema that is developed. Developers of non-W3C technologies may use the schema to publish their own techniques documents that show how to use their technologies to conform to WCAG 2.0. Therefore, while the Techniques documents are specifically created to meet WCAG 2.0 requirements, the structure is intended to be generalizable to other working groups and technologies.

2. Definitions

[Definition: Testable: Either Machine Testable or Reliably Human Testable.]

[Definition: Machine Testable: There is a known algorithm (regardless of whether that algorithm is known to be implemented in tools) that will determine, with complete reliability, whether the technique has been implemented or not. Probabilistic algorithms are not sufficient.]

[Definition: Reliably Human Testable: The technique can be tested by human inspection and it is believed that at least 80% of knowledgeable human evaluators would agree on the conclusion. The use of probabilistic machine algorithms may facilitate the human testing process but this does not make it machine testable.]

[Definition: Not Reliably Testable: The technique is subject to human inspection but it is not believed that at least 80% of knowledgeable human evaluators would agree on the conclusion.]

3. General Requirements

Intended Uses

  • Techniques must be usable by a variety of audiences. Audiences that have been identified include

    • Content developers

    • User agent developers

    • Evaluation tool developers

    • Authoring tool developers

    • Assistive technology developers

    • Training material developers

    • Guidelines developers

    • Operating System developers

  • Source files must be structured in such a way that multiple views can be achieved. A list of specific views is provided in Appendix 1 Output Formats . Some views may be targeted to specific audiences and other views may be appropriate for multiple audiences.

Scope of Documents

  • Techniques should be grouped by particular technologies to which they apply (e.g., HTML, CSS, SVG, ECMAScript).

  • General Techniques - a separate group of techniques that are not related to a specific technology - will be included.

  • Where technologies work together (e.g., HTML and CSS), relevant joint techniques must be presented with the host technology (e.g., HTML). If techniques do not involve interactions between the two technologies, they must be presented with their respective technology only.

    NOTE: There is not consensus about whether it should be permissable to create techniques for technologies that cannot meet the minimum Success Criteria of the guidelines even in combination with other technologies.

  • Techniques must state to which versions of the technology they apply, (i.e., describe a practice to avoid or follow). They may specify all versions, all versions prior to or later than a particular version, or enumerate particular versions.

  • For a given technology, it is not necessary to provide techniques for every Checkpoint if the Checkpoint is not applicable to the technology, either because the technology is designed to be used with another technology (e.g., CSS with HTML) or because it is not possible to achieve full guideline conformance with the technology. In place of a technique there must be an indication that states whether the technology is intended to interact with other technologies to provide full guideline conformance, or whether it is not possible in that technology to achieve guideline conformance for that Success Criterion. In the latter case, outputs must prominently state that full guideline conformance is not possible with the technology.

    NOTE: There is serious debate about whether it should be possible to create views which contain Checklist items related specifically to technologies that do not themselves fully support the guidelines. For example, it may be possible to create a Checklist devoted solely to CSS, but it is never possible to achieve full guideline conformance with CSS. It may be desirable to require that views for such technologies always include other technologies, such as HTML, that can result in complete guideline conformance when following the guidance of that view. It is expected that the process of developing techniques and views will help clarify and close this issue.

  • Techniques may describe practices that are not yet supported by user agents, authoring tools, etc. in order to provide guidance for tool developers. When possible techniques should also describe practices that work in contemporary tools.

  • Information about user agent support for techniques must be provided. At a minimum it is required to state whether the technique is known to be implemented in any existing user agent. For techniques in which current user agent support is known to be variable or otherwise relevant to the technique, that information should also be provided. Additional user agent information may be provided in external resources.


  • Techniques must be highly structured and largely machine manipulable. It is expected that they will exist in XML files conforming to the DTD/Schema in Appendix 3 Techniques Schema .

  • Techniques documents must be versioned in such a way that updates to the documents do not break interdependencies that may exist among multiple documents (e.g., on Core techniques, HTML dependent on CSS, etc.). Versioning can be based on revision dates of specific documents.

  • Each technique must be assigned a unique identifier to enable machine-readable conformance statements.

  • Structure should be general enough that it can be used by groups outside the WAI domain.

  • It must be possible for Techniques documents to be localized.

  • It must be possible to provide techniques that are applicable to specific locales, but are not relevant in other locales.

Relation to WCAG 2.0

  • Each technique must map to a specific WCAG 2.0 Success Criterion or Additional Idea by URI and number for clarity and to enable auto generation of hybrid Guidelines/Techniques documents.

  • There may be multiple techniques for each Success Criterion or Additional Idea, clearly stated that they are alternate techniques.

  • Each technique must state whether its implementation fully meets the Success Criterion or Additional Ideas and if not provide references to other techniques (in the same or other Techniques documents) needed to complete the implementation.

4. Techniques Requirements

The following points are mandatory requirements for Techniques.

5. Checklist Requirements

The following points are mandatory requirements for Checklists.

6. Test File Requirements

The following points are mandatory requirements for Test Files.

Appendix 1 Output Formats

The Techniques are designed to meet a number of needs. As documents are designed to work together, each view may be drawn from multiple source files. The number of possible output formats is therefore large and many views may be generated from the source files at request time.

The following output formats have been identified and it must be possible to generate each of these documents.

NOTE: This list is not yet complete. While it does not have to be for us to proceed with the work, the more complete it is the more likely we will be to not miss anything. Also, it is not clear whether this should be an Appendix (in which case it may be ok to view it as a growing list) or part of the requirements, in which case it probably does need to be considered complete at the time the requirements are ratified.

Appendix 2 Fields

The following granualar units of information have been identified to meet the requirements above.

[To be provided]

Appendix 3 Techniques Schema

[To be provided]