ARIA required owned elements

  • Rule Type:atomic
  • Rule Id: bc4a75
  • 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 has at least one of its required owned elements.

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 required owned elements, except if one of the following is true:

Expectation

Each test target only owns elements with a semantic role from the required owned element list for the test target's semantic role.

Note: The definition of owned by used in this rule is different than the definition of "owned element" in WAI-ARIA. See more in the owned by definition.

Assumptions

If the explicit semantic role on the target element is incorrectly used, and any relationships between elements are already programmatically determinable, failing this rule may not result in accessibility issues for users of assistive technologies, and it should then not be considered a failure under 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.
  • Assistive technologies are not consistent in how they handle situations where a required owned element has a missing or incorrect role. This can lead to situations where inaccurate owned elements behave as expected in one assistive technology, but not in another.
  • Some user agents treat the value of aria-busy as case-sensitive.

Background

Some required owned elements are only valid if they themselves own (or "contain") elements with a given semantic role. This is denoted by an arrow (meaning "containing") in the role description. For example, the role menu has group → menuitemradio as one of its required owned elements, meaning that elements with a role of menu may only own elements with a role of group who themselves only own elements with a role of menuitemradio.

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 owned elements. The Digital Publishing WAI-ARIA Module (DPUB ARIA) 1.0 only has three roles with required owned elements (doc-bibliography, doc-endnotes and doc-glossary); they have issues with their use of role inheritance, and all of them have no required owned elements in the Digital Publishing WAI-ARIA Module (DPUB ARIA) 1.1 editor's draft.

The combobox role is excluded from this rule, because the design pattern for it as described in ARIA 1.1 has proven problematic. The combobox will be significantly different for ARIA 1.2, where it does not have required owned elements.

Note: Subclass roles of required owned elements are not automatically included as possible required owned elements. For example, the treeitem role is not a required owned elements for list, even though treeitem is a subclass role of listitem.

Test Cases

Passed

Passed Example 1

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This element with the list role only owns elements with the listitem role. The listitem role is one of the required owned elements for list.

<div role="list">
	<span role="listitem">Item 1</span>
	<span role="listitem">Item 2</span>
</div>

Passed Example 2

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This element with the tablist role only owns elements with the tab role. The tab role is one of the required owned elements for tablist.

<ul role="tablist">
	<li role="tab">Tab 1</li>
	<li role="tab">Tab 2</li>
</ul>

Passed Example 3

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This element with the grid role only owns elements with the row role, and the element with the row role only owns elements with the cell role. The row role is one of the required owned elements for grid, and cell is one of the required owned elements for row.

<table role="grid">
	<tr role="row">
		<span role="cell">Item 1</span>
	</tr>
</table>

Passed Example 4

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This element with the menu role only owns elements with the menuitem, menuitemradio and menuitemcheckbox role. These roles are all required owned elements for menu. The element with the none role is not owned by the menu because it is not included in the accessibility tree.

<div role="menu">
	<li role="none"></li>
	<li role="menuitem">Item 1</li>
	<div role="menuitemradio" aria-checked="false">Item 2</div>
	<div role="menuitemcheckbox" aria-checked="false">Item 3</div>
</div>

Passed Example 5

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This element with the list role only owns elements with the listitem role through the aria-owns attribute. The listitem role is one of the required owned elements for list.

Note: This test case follows the definition of owned by. If implemented differently, this definition could cause differences in outcome of this test case.

<div role="list" aria-owns="id1"></div>
<div id="id1" role="listitem">Item 1</div>

Passed Example 6

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This element with the list role only owns elements with the listitem role, or elements with the group role, in which each element has the listitem role. Both the listitem role on its own, and the group role (when containing elements with the listitem role) are required owned elements for list.

<div role="list">
	<span role="listitem">Item 1</span>
	<div role="group">
		<span role="listitem">Item 2</span>
		<span role="listitem">Item 3</span>
	</div>
</div>

Failed

Failed Example 1

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This element with the list role owns an element without any of its required owned elements (listitem or group containing listitem).

<div role="list">
	<span>Item 1</span>
</div>

Failed Example 2

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This element with the tablist role owns an element with the listitem role. The listitem role is not one of the required owned elements for tablist.

<ol role="tablist">
	<li role="listitem">Item 1</li>
</ol>

Failed Example 3

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This element with the list role owns an element with the listitem role, and one with the link role. The link role is not one of the required owned elements for list.

<div role="list">
	<li>Item 1</li>
	<span role="link">Item 2</span>
</div>

Failed Example 4

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This element with the grid role only owns elements with the row role, but the element with the row role does not own elements with the cell role. The cell is one of the required owned elements for row.

<div role="grid">
	<div role="row">
		<span>Item 1</span>
	</div>
</div>

Failed Example 5

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This element with the list role owns an element with the tab role through the aria-owns attribute. The tab role is not one of the required owned elements for list.

Note: This test case follows the definition of owned by. If implemented differently, this definition could cause differences in outcome of this test case.

<div role="list" aria-owns="id2"></div>
<div id="id2" role="tab">Tab 1</div>

Failed Example 6

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This element with the list role owns an element with the group role, but the group owns elements with the tab role. The group is not a required owned elements for list, if it owns elements with a semantic role other then listitem.

<div role="list">
	<div role="group">
		<span role="tab">Item 1</span>
		<span role="tab">Item 2</span>
	</div>
</div>

Inapplicable

Inapplicable Example 1

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This element with the list role is not included in the accessibility tree because the aria-hidden attribute is set to true.

<div role="list" aria-hidden="true"></div>

Inapplicable Example 2

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This ul element does not have an explicit semantic role.

<ul>
	<li>Item 1</li>
</ul>

Inapplicable Example 3

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This element with the progressbar role does not need required owned elements.

<div role="progressbar" aria-valuenow="20" aria-valuemin="0" aria-valuemax="100">20 %</div>

Inapplicable Example 4

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This element with the menu role has attribute an aria-busy attribute set to true.

<ul role="menu" aria-busy="true">
	Loading
</ul>

Inapplicable Example 5

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This element with the combobox role conforms to WAI-ARIA 1.1 without owned elements.

<label for="combo">My Combobox</label> <input role="combobox" aria-expanded="false" id="combo" />

Glossary

Attribute value

The attribute value of a content attribute set on an HTML element is the value that the attribute gets after being parsed and computed according to specifications. It may differ from the value that is actually written in the HTML code due to trimming whitespace or non-digits characters, default values, or case-insensitivity.

Some notable case of attribute value, among others:

  • For enumerated attributes, the attribute value is either the state of the attribute, or the keyword that maps to it; even for the default states. Thus <input type="image" /> has an attribute value of either Image Button (the state) or image (the keyword mapping to it), both formulations having the same meaning; similarly, "an input element with a type attribute value of Text" can be either <input type="text" />, <input /> (missing value default), or <input type="invalid" /> (invalid value default).
  • For boolean attributes, the attribute value is true when the attribute is present and false otherwise. Thus <button disabled>, <button disabled="disabled"> and <button disabled=""> all have a disabled attribute value of true.
  • For attributes whose value is used in a case-insensitive context, the attribute value is the lowercase version of the value written in the HTML code.
  • For attributes that accept numbers, the attribute value is the result of parsing the value written in the HTML code according to the rules for parsing this kind of number.
  • For attributes that accept sets of tokens, whether space separated or comma separated, the attribute value is the set of tokens obtained after parsing the set and, depending on the case, converting its items to lowercase (if the set is used in a case-insensitive context).
  • For aria-* attributes, the attribute value is computed as indicated in the WAI-ARIA specification and the HTML Accessibility API Mappings.

This list is not exhaustive, and only serves as an illustration for some of the most common cases.

The attribute value of an IDL attribute is the value returned on getting it. Note that when an IDL attribute reflects a content attribute, they have the same attribute value.

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
QualWebconsistentYesView Report
SortSiteconsistentYesView Report

Acknowledgments

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