Proposed Test Rule: Heading is descriptive

Description

This rule checks that headings describe the topic or purpose of the content.

Applicability

This rule applies to any element with the semantic role of heading that is either visible or included in the accessibility tree.

Expectation 1

Each target element which is visible describes the topic or purpose of the first palpable content which is non-decorative, visible, and after the target in tree order in the flat tree.

Expectation 2

Each target element which is included in the accessibility tree describes the topic or purpose of the first palpable content which is non-decorative, included in the accessibility tree, and after the target in tree order in the flat tree.

Note: Headings do not need to be lengthy. A word, or even a single character, may suffice.

Assumptions

This rule assumes that the language of each test target can be correctly determined (either programmatically or by analyzing the content), and sufficiently understood.
This rule assumes that the flat tree order is close to the reading order, as elements are rendered on the page. Due to positioning, it is possible to render a document in a order that greatly differ from the tree order, in which case the content which is visually associated with a heading might not be the content following it in tree order and this rule might fail while Success Criterion 2.4.6 Headings and Label is still satisfied.

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 heading and fail this rule with some technology but users of other technologies would not experience any accessibility issue.

Background

Test Cases

Passed

Passed Example 1

Heading marked up with h1 element that describes the topic or purpose of the following palpable content.

<html lang="en">
	<h1>Opening Hours</h1>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Passed Example 2

Heading marked up with role="heading" that describes the topic or purpose of the following palpable content.

<html lang="en">
	<span role="heading" aria-level="1">Opening Hours</span>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Passed Example 3

Heading marked up with role="heading" that describes the topic or purpose of the following palpable content, with a default aria-level assigned.

<html lang="en">
	<span role="heading">Opening Hours</span>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Passed Example 4

Heading marked up with h1 element with an image that describes the topic or purpose of the following palpable content.

<html lang="en">
	<h1>
		<img scr="/test-assets/descriptive-heading-b49b2e/opening_hours_icon.png" alt="Opening hours" />
	</h1>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Passed Example 5

Heading marked up with h1 element that is a single character that describes the topic or purpose of the following palpable content.

<html lang="en">
	<h1>A</h1>
	<dl>
		<dt>airplane</dt>
		<dd>
			a powered flying vehicle with fixed wings and a weight greater than that of the air it displaces.
		</dd>
		<dt>apple</dt>
		<dd>
			the round fruit of a tree of the rose family, which typically has thin green or red skin and crisp flesh.
		</dd>
	</dl>
</html>

Passed Example 6

Heading marked up with role="heading" that describes the topic or purpose of the following palpable content. The heading is positioned off screen and is included in the accessibility tree.

<html lang="en">
	<span role="heading" aria-level="1" style="position: absolute; top: -9999px; left: -9999px;">Opening Hours</span>
	<p style="position: absolute; top: -9999px; left: -9999px;">
		We are open Monday through Friday from 10 to 16
	</p>
</html>

Passed Example 7

Heading marked up with h1 element that describes the topic or purpose of the following palpable content. The heading is visible, but is not included in the accessibility tree.

<html lang="en">
	<h1 aria-hidden="true">Opening Hours</h1>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Passed Example 8

This heading describes the first palpable content after it (the first p element). The next palpable content (the second p element) is not considered by this rule.

<html lang="en">
	<h1>Opening Hours</h1>
	<p>We are open Monday through Friday from 10 to 16</p>
	<p>We are open Saturday from 10 to 13</p>
</html>

Failed

Failed Example 1

Heading marked up with h1 element that does not describe the topic or purpose of the following palpable content.

<html lang="en">
	<h1>Weather</h1>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Failed Example 2

Heading marked up with role="heading" that does not describe the topic or purpose of the following palpable content.

<html lang="en">
	<span role="heading" aria-level="1">Weather</span>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Failed Example 3

Heading marked up with role="heading" that does not describe the topic or purpose of the following palpable content. The heading is positioned off screen and is included in the accessibility tree.

<html lang="en">
	<span role="heading" style="position: absolute; top: -9999px; left: -9999px;">Weather</span>
	<p style="position: absolute; top: -9999px; left: -9999px;">
		We are open Monday through Friday from 10 to 16
	</p>
</html>

Failed Example 4

Heading marked up with h1 element that does not describe the topic or purpose of the following palpable content. The heading is visible, but is not included in the accessibility tree.

<html lang="en">
	<h1 aria-hidden="true">Weather</h1>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Failed Example 5

This heading does not describe the first palpable content after it (the first p element). The next palpable content (the second p element) is not considered by this rule.

<html lang="en">
	<h1>Weather</h1>
	<p>We are open Monday through Friday from 10 to 16</p>
	<p>It is going to rain tomorrow</p>
</html>

Inapplicable

Inapplicable Example 1

No heading.

<html lang="en">
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Inapplicable Example 2

Heading that is neither visible to users, nor included in the accessibility tree.

<html lang="en">
	<h1 style="display: none;">Opening hours</h1>
	<p>We are open Monday through Friday from 10 to 16</p>
</html>

Inapplicable Example 3

Empty heading marked up with h1 is not visible.

<html lang="en">
	<h1></h1>
</html>

Inapplicable Example 4

Empty heading marked up with role="heading" is not visible.

<html lang="en">
	<p role="heading" aria-level="1"></p>
</html>

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.

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.

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.

Visible

Content perceivable through sight.

Content is considered visible if making it fully transparent would result in a difference in the pixels rendered for any part of the document that is currently within the viewport or can be brought into the viewport via scrolling.

Content is defined in WCAG.

For more details, see examples of visible.

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

There are currently no known implementations for this rule. If you would like to contribute an implementation, please read the ACT Implementations page for details.

Changelog

This is the first version of this ACT rule.