ARIA required context role

  • Rule Type:atomic
  • Rule Id: ff89c9
  • Last modified: Nov 05, 2020
  • Accessibility Requirements Mapping:
    • 1.3.1 Info and Relationships (Level A)
      • Learn More about 1.3.1 Info and Relationships
      • Required for conformance to WCAG 2.0 and later on level A and higher.
      • Outcome mapping:
        • Any failed outcomes: success criterion is not satisfied.
        • All passed outcomes: success criterion needs further testing.
        • An inapplicable outcome: success criterion needs further testing.

Description

This rule checks that an element with an explicit semantic role exists inside its required context.

Applicability

The rule applies to any HTML or SVG element that is included in the accessibility tree and has a WAI-ARIA 1.1 explicit semantic role with a required context role, except if the element has an implicit semantic role that is identical to its explicit semantic role.

Expectation

Each test target is owned by an element that has a semantic role that is one of the required context roles of the target element.

Assumptions

This rule assumes that the role attribute is used to give a semantic role to the element according to ARIA specifications. If it is used for other purposes, and relationships between elements are already programmatically determinable by other means, it is possible to fail this rule but still satisfy WCAG success criterion 1.3.1 Info and Relationships.

Accessibility Support

  • User agents do not all have the same accessibility tree. Particularly the method of deriving which element owns which other elements varies between browsers. This can lead to different results for this rule, depending on which accessibility tree is used as input.
  • aria-owns has limited support in some user agents.
  • There exist some combination of popular browsers and assistive technologies who do not announce correctly relationships based on a mix of implicit and explicit roles.

Background

The applicability of this rule is limited to the WAI-ARIA 1.1 Recommendation roles. The WAI-ARIA Graphics Module does not include any required context roles. The Digital Publishing WAI-ARIA Module (DPUB ARIA) 1.0 only has two roles with required context roles (doc-biblioentry and doc-endnote); both of them have issues with their use of role inheritance, and both of them are deprecated in the Digital Publishing WAI-ARIA Module (DPUB ARIA) 1.1 editor's draft.

An example of an element that has an implicit semantic role that is identical to its explicit semantic role is a <li role="listitem"> element. These elements are not applicable because they have extra requirements and should thus be checked separately.

The definition of owned by used in this rule is different from the definition of "owned element" in WAI-ARIA.

Subclass roles of required context roles are not automatically included as possible required context roles. For example, the feed role is not a possible required context role for listitem, even though feed is a subclass role of the list role.

Some user agents try to correct missing required context roles or incorrect content model. This often results, for example, in an isolated list item being presented as part of a one-item list containing only itself. Therefore, most test cases contain several targets to try and circumvent these corrections in order to better demonstrate the issue.

Test Cases

Passed

Passed Example 1

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These elements with an explicit role of listitem are owned by an element with their required context role, list, expressed as an explicit role.

<div role="list">
	<div role="listitem">List item 1</div>
	<div role="listitem">List item 2</div>
</div>

Passed Example 2

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These elements with an explicit role of listitem are owned by an element with their required context role, list, expressed as an implicit role of ul. Note that this test case does not satisfy Success Criterion 4.1.1 Parsing because the ul element does not respect its content model.

<ul>
	<div role="listitem">List item 1</div>
	<div role="listitem">List item 2</div>
</ul>

Passed Example 3

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These elements with an explicit role of listitem are owned by an element with their required context role even though they are not direct DOM children of it. ARIA ownership "skips" through presentational nodes because they are not included in the accessibility tree.

<div role="list">
	<div role="presentation">
		<div role="listitem">List item 1</div>
		<div role="listitem">List item 2</div>
	</div>
</div>

Passed Example 4

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These elements with an explicit role of listitem are owned by an element with their required context role even though they are not DOM descendants of it. The aria-owns attribute is used to alter the accessibility tree and place the target elements in their required context role.

<div role="list" aria-owns="item1 item2"></div>
<div id="item1" role="listitem">List item 1</div>
<div id="item2" role="listitem">List item 2</div>

Passed Example 5

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These elements with an explicit role of listitem are owned by an element with their required context role even though they are not direct DOM descendants of it. The aria-owns attribute is used to alter the accessibility tree and place the target elements in their required context role.

<div role="list" aria-owns="item1 item2">
	<div role="navigation">
		<div id="item1" role="listitem">List item 1</div>
		<div id="item2" role="listitem">List item 2</div>
	</div>
</div>

Passed Example 6

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These elements with an explicit role of listitem are owned by an element with their required context role because implicit ownership (inherited from DOM tree structure) crosses shadow boundaries.

<div id="host" role="list"></div>

<script>
	const host = document.querySelector('#host')
	const root = host.attachShadow({ mode: 'open' })
	root.innerHTML = '<div role="listitem">List item 1</div> <div role="listitem">List item 2</div>'
</script>

Failed

Failed Example 1

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This element with an explicit role of listitem is not owned by an element with its required context role.

<div role="listitem">List item 1</div>

Failed Example 2

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These elements with an explicit role of listitem are not owned by an element with their required context role. They are owned by the tabpanel element, because it is the closest ancestor.

<div role="list">
	<div role="tabpanel">
		<div role="listitem">List item 1</div>
		<div role="listitem">List item 2</div>
	</div>
</div>

Failed Example 3

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These elements with an explicit role of listitem are not owned by an element with their required context role. They are instead owned by the div with an aria-label attribute; even though this div has no role, it has a global ARIA attribute and is thus included in the accessibility tree.

<div role="list">
	<div aria-label="menu">
		<div role="listitem">List item 1</div>
		<div role="listitem">List item 2</div>
	</div>
</div>

Failed Example 4

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These elements with an explicit role of listitem are not owned by an element with their required context role because explicit ownership (set by aria-owns) does not cross shadow boundaries.

<div role="list" aria-owns="item1 item2"></div>

<div id="host"></div>

<script>
	const host = document.querySelector('#host')
	const root = host.attachShadow({ mode: 'open' })
	root.innerHTML = '<div id="item1" role="listitem">List item 1</div> <div id="item2" role="listitem">List item 2</div>'
</script>

Inapplicable

Inapplicable Example 1

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This element with an explicit role of listitem is not included in the accessibility tree.

<div role="listitem" style="display:none;">List item 1</div>

Inapplicable Example 2

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There is no element with an explicit role.

<ul>
	<li>List item 1</li>
</ul>

Inapplicable Example 3

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This section element with an explicit role of doc-abstract has a role from the Digital Publishing WAI-ARIA Module (DPUB ARIA) 1.0, not the WAI-ARIA 1.1 Recommendation.

<section role="doc-abstract" aria-label="Abstract">
	<p>Accessibility of web content requires semantic information about widgets, structures, and behaviors …</p>
</section>

Inapplicable Example 4

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There is no element whose role has required context role because the header role does not have one.

<div role="header" aria-level="1">Hello!</div>
<p>Welcome to my homepage!</p>

Inapplicable Example 5

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There is no element with an explicit role different from its implicit role. This li element has an explicit role of listitem which is identical to its implicit role.

<ul>
	<li role="listitem">List item 1</li>
</ul>

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.

Owned by

An element A is owned by element B if element A is a child of element B in the accessibility tree.

Being a child in the accessibility tree is different from being a child in the DOM tree. Some DOM nodes have no corresponding node in the accessibility tree (for example, because they are marked with role="presentation"). A child in the accessibility tree can thus correspond to a descendant in the DOM tree. Additionally, the use of aria-owns attribute can change the tree structure to something which is not a subtree of the DOM tree.

This definition is different from the definition of "owned element" in WAI-ARIA. Because browsers have different accessibility trees, which element owns which other elements can vary between browsers. Until there is a standard accessibility tree, testing with multiple accessibility trees may be necessary.

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).

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
AlfaconsistentYesView Report
SortSiteconsistentYesView Report
axe-corepartially-consistentYesView Report
QualWebpartially-consistentYesView Report

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