role attribute has valid value

  • Rule Type:atomic
  • Rule Id: 674b10
  • Last modified: Sep 23, 2020
  • Accessibility Requirements Mapping:
    • ARIA 1.1, 5.4 Definition of Roles
      • Learn More about ARIA 1.1, 5.4 Definition of Roles
      • Not required to conformance to any W3C accessibility recommendation.
      • Outcome mapping:
        • Any failed outcomes: WAI-ARIA requirement is not satisfied.
        • All passed outcomes: WAI-ARIA requirement needs further testing.
        • An inapplicable outcome: WAI-ARIA requirement is satisfied.
    • ARIA Graphics module 1.0, 4.1 Definition of Roles
      • Learn More about ARIA Graphics module 1.0, 4.1 Definition of Roles
      • Not required to conformance to any W3C accessibility recommendation.
      • Outcome mapping:
        • Any failed outcomes: WAI-ARIA Graphics Module requirement is not satisfied.
        • All passed outcomes: WAI-ARIA Graphics Module requirement needs further testing.
        • An inapplicable outcome: WAI-ARIA Graphics Module requirement is satisfied.
    • ARIA Digital Publishing module 1.0, 4.1 Definition of Roles
      • Learn More about ARIA Digital Publishing module 1.0, 4.1 Definition of Roles
      • Not required to conformance to any W3C accessibility recommendation.
      • Outcome mapping:
        • Any failed outcomes: WAI-ARIA Digital Publishing Module requirement is not satisfied.
        • All passed outcomes: WAI-ARIA Digital Publishing Module requirement needs further testing.
        • An inapplicable outcome: WAI-ARIA Digital Publishing Module requirement is satisfied.
    • ARIA4: Using a WAI-ARIA role to expose the role of a user interface component
      • Learn More about technique ARIA4
      • Not required to conformance to any W3C accessibility recommendation.
      • Outcome mapping:
        • Any failed outcomes: technique is not satisfied.
        • All passed outcomes: technique needs further testing.
        • An inapplicable outcome: technique needs further testing.
    • G108: Using markup features to expose the name and role, allow user-settable properties to be directly set, and provide notification of changes
      • Learn More about technique G108
      • Not required to conformance to any W3C accessibility recommendation.
      • Outcome mapping:
        • Any failed outcomes: technique is not satisfied.
        • All passed outcomes: technique needs further testing.
        • An inapplicable outcome: technique needs further testing.
  • Input Aspects:

Description

This rule checks that each role attribute has a valid value.

Applicability

Any role attribute for which all the following are true:

Expectation

Each test target has at least one token which is a valid value corresponding to a non-abstract role from WAI-ARIA Specifications.

Assumptions

There are currently no assumptions

Accessibility Support

Older browsers do not support more than one token in the value for a role attribute. If multiple values are used in the role attribute, the attribute is ignored in these browsers.

Background

The role attribute is a set of space separated tokens. Having a whitespace separated list of more than one token in the value of the role attribute is used for what is known as fallback roles. If the first token is not accessibility supported (or valid), the next one will be used for determining the semantic role of the element, and so forth. Having the rule target attributes containing at least one non-ASCII whitespace character ensures that there is at least one token in the set.

Further reading:

Test Cases

Passed

Passed Example 1

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This role attribute contains one token, and this token is a valid WAI-ARIA role.

<input type="text" role="textbox" />

Passed Example 2

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This role attribute contains two tokens, and these tokens are both valid WAI-ARIA roles.

<span role="button link" onclick="location.href='https://act-rules.github.io/'">ACT rules</span>

Passed Example 3

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This role attribute contains two tokens, and one of these tokens (img) is a valid WAI-ARIA role.

<img role="image img" src="/test-assets/shared/w3c-logo.png" alt="W3C logo" />

Failed

Failed Example 1

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This role attribute contains one token, but this token is not a valid role in any of the WAI-ARIA specifications.

<img role="lnik" src="/test-assets/shared/w3c-logo.png" alt="W3C logo" onclick="location.href='https://www.w3.org/'" />

Failed Example 2

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This role attribute contains two tokens, but none of these tokens is a valid role in any of the WAI-ARIA specifications.

<img
	role="lnik buton"
	src="/test-assets/shared/w3c-logo.png"
	alt="W3C logo"
	onclick="location.href='https://www.w3.org/'"
/>

Inapplicable

Inapplicable Example 1

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There is no role attribute.

<img src="/test-assets/shared/w3c-logo.png" alt="W3C logo" />

Inapplicable Example 2

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This role attribute has no value.

<div role>Some Content</div>

Inapplicable Example 3

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This role attribute is empty ("").

<div role="">Some Content</div>

Inapplicable Example 4

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This role attribute is only ASCII whitespace.

<input type="text" role=" " />

Inapplicable Example 5

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This role attribute is specified on an element which is not included in the accessibility tree.

<div aria-hidden="true" role="banner">Some Content</div>

Glossary

Explicit Semantic Role

The explicit semantic role of an element is determined by its role attribute (if any).

The role attribute takes a list of tokens. The explicit semantic role is the first valid role in this list. The valid roles are all non-abstract roles from WAI-ARIA Specifications. If the element has no role attribute, or if it has one with no valid role, then this element has no explicit semantic role.

Other roles may be added as they become available. Not all roles will be supported in all assistive technologies. Testers are encouraged to adjust which roles are allowed according to the accessibility support base line. For the purposes of executing test cases in all rules, it should be assumed that all roles are supported by assistive technologies so that none of the roles fail due to lack of accessibility support.

Accessibility Support for Explicit Semantic Role

Some browsers and assistive technologies treat the tokens of the role attribute as case-sensitive. Unless lowercase letters are used for the value of the role attribute, not all user agents will be able to interpret the tokens correctly. ARIA in HTML (working draft) also specifies that authors must use lowercase letters for the role and aria-* attributes.

Hidden State

An HTML element's hidden state is "true" if at least one of the following is true for itself or any of its ancestors in the flat tree:

  • has a hidden attribute; or
  • has a computed CSS property display of none; or
  • has a computed CSS property visibility of hidden; or
  • has an aria-hidden attribute set to true

In any other case, the element's hidden state is "false".

Implicit Semantic Role

The implicit semantic role of an element is a pre-defined value given by the host language which depends on the element and its ancestors.

Implicit roles for HTML and SVG, are documented in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

Accessibility Support for Implicit Semantic Role

  • Images with an empty alt attribute should have an implicit role of presentation, according to the HTML Accessibility API Mapping (work in progress). However, there are several popular browsers that do not treat images with empty alt attribute as having a role of presentation. Instead, they add the img element to the accessibility tree with a role of either img or graphic.

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs. Elements in the accessibility tree are exposed to assistive technologies, allowing users to interact with the elements in a way that meet the requirements of the individual user.

The general rules for when elements are included in the accessibility tree are defined in the core accessibility API mappings. For native markup languages, such as HTML and SVG, additional rules for when elements are included in the accessibility tree can be found in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

For more details, see examples of included in the accessibility tree.

Note: Users of assistive technologies might still be able to interact with elements that are not included in the accessibility tree. An example of this is a focusable element with an aria-hidden attribute with a value of true. Such an element could still be interacted using sequential keyboard navigation regardless of the assistive technologies used, even though the element would not be included in the accessibility tree.

Marked as decorative

An element is marked as decorative if one of the following conditions is true:

  • it has an explicit role of none or presentation; or
  • it is an img element with an alt attribute whose value is the empty string (alt=""), and with no explicit role.

Elements are marked as decorative as a way to convey the intention of the author that they are pure decoration. It is different from the element actually being pure decoration as authors may make mistakes. It is different from the element being effectively ignored by assistive technologies as rules such as presentational roles conflict resolution may overwrite this intention.

Elements can also be ignored by assistive technologies if their hidden state is true. This is different from marking the element as decorative and does not convey the same intention. Notably, the hidden state of an element may change as users interact with the page (showing and hiding elements) while being marked as decorative should stay the same through all states of the page.

Outcome

An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

  • Inapplicable: No part of the test subject matches the applicability
  • Passed: A test target meets all expectations
  • Failed: A test target does not meet all expectations

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such "interim" results can be expressed with the incomplete outcome.

Semantic Role

The semantic role of an element is determined by the first of these cases that applies:

  1. Conflict If the element is marked as decorative, but the element is included in the accessibility tree; or would be included in the accessibility tree when its hidden state is false, then its semantic role is its implicit role.
  2. Explicit If the element has an explicit role, then its semantic role is its explicit role.
  3. Implicit The semantic role of the element is its implicit role.

Accessibility Support for Definition of Semantic Role for Semantic Role

  • There exist popular web browsers and assistive technologies which do not correctly implement Presentational Roles Conflict Resolution. These technologies will not include in the accessibility tree elements that should be, according to Specifications. Thus, some elements that should have their semantic role fixed by case Conflict above are instead falling into case Explicit and are hidden for users of assistive technologies.
  • A similar conflict exists for focusable elements with a aria-hidden="true" attribute. The WAI ARIA specification does not explain how to solve it. Some browsers give precedence to the element being focusable (and expose it in the accessibility tree) while some give precedence to the aria-hidden attribute (and hide the element).

Whitespace

Whitespace are characters that have the Unicode "White_Space" property in the Unicode properties list.

This includes:

  • all characters in the Unicode Separator categories, and
  • the following characters in the Other, Control category:

    • Character tabulation (U+0009)
    • Line Feed (LF) (U+000A)
    • Line Tabulation (U+000B)
    • Form Feed (FF) (U+000C)
    • Carriage Return (CR) (U+000D)
    • Next Line (NEL) (U+0085)

Useful Links


Implementations

This section is not part of the official rule. It is populated dynamically and not accounted for in the change history or the last modified date. This section will not be included in the rule when it is published on the W3C website.

ToolConsistencyCompleteReport
axe-coreconsistentYesView Report
QualWebconsistentYesView Report
SortSiteconsistentYesView Report

Acknowledgments

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