Proposed Test Rule: ARIA state or property is permitted

Description

This rule checks that WAI-ARIA states or properties are allowed for the element they are specified on.

Applicability

This rule applies to any WAI-ARIA state or property that is specified on an HTML or SVG element that is included in the accessibility tree.

Expectation

For each test target, one of the following is true:

global: the test target is a global state or property; or
semantic Role: the test target is an inherited, supported, or required state or property of the semantic role of the element on which the test target is specified; or
language feature: the test target is specified on an HTML element and is allowed on that element. Which ARIA states or properties may be used on which element is described in ARIA in HTML.

Assumptions

There are currently no assumptions

Accessibility Support

Implementation of Presentational Roles Conflict Resolution varies from one browser or assistive technology to another. Depending on this, some elements can have a semantic role of none and their attributes fail this rule with some technologies but users of other technology would not experience any accessibility issue.

Background

In HTML, there are language features that do not have corresponding implicit WAI-ARIA semantics. As per ARIA in HTML Editor’s Draft, those elements can have global states or properties. Some of those elements can also have inherited, supported, or required states or properties that correspond to a WAI-ARIA role. For example, the audio element has no corresponding ARIA semantics but it can have inherited, supported, or required states or properties of the application role.

Assessing the value of the attribute is out of scope for this rule.

Test Cases

Passed

Passed Example 1

The aria-pressed state is supported for the semantic role button, which is the implicit role for button elements.

<button aria-pressed="false">My button</button>

Passed Example 2

The aria-pressed state is supported for the semantic role button, which is the explicit role of this div element.

<div role="button" aria-pressed="false">My button</div>

Passed Example 3

The aria-busy state is a global state that is supported by all elements, even without any semantic role.

<div aria-busy="true">My busy div</div>

Passed Example 4

The aria-label property is a global property and thus inherited for all semantic role.

<div role="button" aria-label="OK">✓</div>

Passed Example 5

The aria-checked state is required for the semantic role checkbox.

<div role="checkbox" aria-checked="false">My checkbox</div>

Passed Example 6

The aria-controls property is required for the semantic role combobox.

<div role="combobox" aria-controls="id1" aria-expanded="false">My combobox</div>

Passed Example 7

The aria-controls property is required for the semantic role combobox. WAI-ARIA states and properties with empty value are still applicable to this rule.

<div role="combobox" aria-expanded="false" aria-controls>My combobox</div>

Passed Example 8

The aria-controls property is required for the semantic role combobox. WAI-ARIA states and properties with empty value (specified as an empty string) are still applicable to this rule.

<div role="combobox" aria-expanded="false" aria-controls="">My combobox</div>

Passed Example 9

The aria-label property is global and thus inherited for all semantic role, including the ones from the WAI-ARIA Graphics Module. This rule is also applicable to SVG elements.

<svg xmlns="http://www.w3.org/2000/svg" role="graphics-object" width="100" height="100" aria-label="yellow circle">
	<circle cx="50" cy="50" r="40" fill="yellow"></circle>
</svg>

Passed Example 10

This button element has an explicit role of none. However, it is focusable (by default). Thus it has a semantic role of button due to Presentational Roles Conflict Resolution. The aria-pressed state is supported for the button role.

<button role="none" aria-pressed="false">ACT rules are cool!</button>

Passed Example 11

This input element does not have an explicit role of textbox, but the aria-required property may be used on an input element with a type attribute value of password.

<label>Password<input type="password" aria-required="true"/></label>

Failed

Failed Example 1

The aria-sort property is neither inherited, supported, nor required for the semantic role button, which is the implicit role for the button element.

<button aria-sort="">Sort by year</button>

Failed Example 2

The aria-orientation property may not be used on audio element, nor it can be used on application (the semantic role for which inherited, supported, or required states or properties are also applicable to audio element).

<audio src="/test-assets/moon-audio/moon-speech.mp3" controls aria-orientation="horizontal"></audio>

Inapplicable

Inapplicable Example 1

This div element has no WAI-ARIA state or property.

<div role="region">A region of content</div>

Inapplicable Example 2

This div element is not included in the accessibility tree, hence its WAI-ARIA state or property is not checked.

<div role="button" aria-sort="" style="display:none;"></div>

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.

Focusable

Elements that can become the target of keyboard input as described in the HTML specification of focusable and can be focused.

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).

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. [examples of included in the accessibility tree]: https://act-rules.github.io/pages/examples/included-in-the-accessibility-tree/

Marked as decorative

An element is marked as decorative if one or more 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.

Namespaced Element

An element with a specific namespaceURI value from HTML namespaces. For example an “SVG element” is any element with the “SVG namespace”, which is http://www.w3.org/2000/svg.

Namespaced elements are not limited to elements described in a specification. They also include custom elements. Elements such as a and title have a different namespace depending on where they are used. For example a title in an HTML page usually has the HTML namespace. When used in an svg element, a title element has the SVG namespace instead.

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:

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.
Explicit If the element has an explicit role, then its semantic role is its explicit role.
Implicit The semantic role of the element is its implicit role.

WAI-ARIA specifications

The WAI ARIA Specifications group both the WAI ARIA W3C Recommendation and ARIA modules, namely:

Note: depending on the type of content being evaluated, part of the specifications might be irrelevant and should be ignored.

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.

Implementation	Consistency	Complete	Report
Alfa	Consistent	No	View Report
Axe-core	Partially-consistent	Yes	View Report
QualWeb	Consistent	Yes	View Report
SortSite	Consistent	No	View Report

Changelog

This is the first version of this ACT rule.