About ACT Rules

What are ACT Rules

ACT Rules are designed to harmonize how edge cases for WCAG and other accessibility guidance are tested. Each ACT Rule describes in technology specific language how to test one particular aspect of a WCAG success criterion or other requirement. Rules have passed, failed, and inapplicable examples which can be used as test cases to determine the consistency of test tools and methodologies.

ACT Rules are Informative

ACT Rules are informative — that means they are not required for determining conformance. The basis for determining conformance to WCAG is the success criteria from the WCAG standard — not the ACT Rules.

While W3C’s List of ACT Rules for WCAG 2 are reviewed by the W3C Accessibility Guidelines Working Group (AGWG), they are not vetted to the same degree as the W3C Web Content Accessibility Guidelines (WCAG) standard (called W3C Recommendation). The WCAG standard is the normative reference on determining conformance.

ACT Rules are Partial Checks

ACT Rules typically check specific accessibility requirement such as the WCAG 2 success criteria. For example, an ACT Rule might test that a table cell has a header, rather than testing success criterion 1.3.1 “Info and Relationships” in its entirety. In fact, this example rule would not even check the validity of the table header, only if the header exists for a given table cell.

ACT Rules are also technology-specific. For example, the aforementioned table header example would be specific to HTML, possibly enriched with WAI-ARIA roles and properties, but not to other technologies with tables. WCAG 2 success criteria are designed to be technology-agnostic and applicable to all web technologies.

ACT Rules Check for Failures

ACT Rules are designed to check failures in satisfying WCAG 2 success criteria and other accessibility requirements. That is, when content fails ACT Rules, it means that the content does not satisfy the corresponding requirement. However, when content passes ACT Rules, it means that no corresponding failures were detected — it does not necessarily mean that the content satisfies all aspects of the corresponding accessibility requirement.

WCAG success criteria typically cover several aspects and technologies, while ACT Rules only check specific aspects. Checking that content satisfies all aspects of WCAG success criteria typically requires further verification by human testers. Requirements for WAI-ARIA are often more atomic than the WCAG 2 success criteria, and can therefore often be fully covered with ACT Rules.

Note: WCAG 2 Conformance Requirement 1 allows for “conforming alternate versions”. That means that content may still conform to WCAG 2, even when content fails ACT Rules.

Implementation of ACT Rules

ACT Rules can be implemented by accessibility test tools and methodologies. Each rule comes with a number of passed, failed, and inapplicable examples. By running the tool or methodology against the examples its consistency with the rule can be determined. Vendors who publish such test results are included in the ACT Rules Implementation in Test Tools and Methodologies List.

Who develops ACT

The ACT Task Force of the W3C Accessibility Guidelines Working Group (AG WG) develops the ACT Rules Format specification. The ACT Task Force also reviews test rules contributed by the community in first instance. Formal publication of the ACT Rules Format specification and of ACT Rules listed on this page is made by AG WG.

The ACT Rules Community Group develops test rules according to the ACT Rules Format specification. These rules by the community group do not have any formal standing in the W3C process.

Opportunities for contributing to ACT and other WAI work are introduced in Participating in WAI.

Structure of ACT Rules

ACT Rules conform to the Accessibility Conformance Testing (ACT) Rules Format 1.0 standard. They include the following parts:

Descriptive Title – title for the ACT Rule, which should describe the rule
Rule Identifier – identifier for the ACT Rule; the rules use alphanumeric strings
Rule Type – there are two basic types of ACT Rules, depending on what is being tested:
- Atomic Rule – test one specific situation, which may be part of a composite rule
- Composite Rule – combine outcome from multiple atomic rules to one outcome
Accessibility Requirements Mapping – maps the ACT Rule to particular accessibility requirements; in this suite of rules we use Web Content Accessibility Guidelines (WCAG) 2 Success Criteria
Rule Input – describes the scope of input into ACT Rules, which is one of the following:
- Input Aspects – input into atomic rules, for example DOM Tree and CSS Styling etc.
- Input Rules – input into the composite rules, which are the atomic rules in scope
Applicability – description of the specific parts of the content, for which the rule applies
Expectations – description of the expected characteristics of the applicable rule content
Assumptions – assumptions made, for example specific interpretations of the requirements
Accessibility Support – known limitations regarding browsers and assistive technology
Examples (Test Cases) – sample code demonstrating passed, failed, and inapplicable rule conditions
Change Log – history of changes for the ACT Rules, to support backward compatibility
Glossary – list of key terms defined by the ACT Rule or used by the specific ACT Rule
Issues List (Optional) – list of known issues or bugs for the particular ACT Rule, if any
Background (Optional) – relevant background, for example additional documentation, if any
Acknowledgements (Optional) – for example rule writers, reviewers, and other contributors