Proposed Links with identical accessible names and same context serve equivalent purpose

Description

This rule checks that links with identical accessible names in the same context resolve to the same or equivalent resources.

Applicability

This rule applies to any set of two or more HTML or SVG elements for which all the following are true:

the elements are inheriting semantic link nodes; and
the elements are in the same web page (HTML); and
the elements are included in the accessibility tree; and
the elements have matching accessible names that are not empty (""); and
have the same programmatically determined link context.

Note: The test target for this rule is the full set of link elements that share the same matching accessible name and programmatically determined link context.

Expectation

When followed, the links in each set of target elements resolve to the same resource or to equivalent resources.

Note: Resolving the links includes potential redirects, if the redirects happen instantly.

Assumptions

This rule assumes that the purpose of the links with identical accessible names and context would not be ambiguous to users in general, which is the exception mentioned in Success Criterion 2.4.4 Link Purpose (In Context). If the links are ambiguous to users in general, users of assistive technologies are not at a disadvantage when viewing the links, which makes it more of a general user experience concern than an accessibility issue.
This rule assumes that, within the context of the test subject, the description provided by the accessible name of a link can only accurately describe one resource (notably, homonyms alone are not used as link names). Thus, if two or more links have the same accessible name but resolve to different resources, at least one of them does not describe its purpose.
This rule assumes that assistive technologies are exposing all links on the page in the same way no matter which document tree they are in. If an assistive technology requires the user to “enter” an iframe or a shadow tree before exposing its links, then it is possible for two links to have identical name and context but resolve to different resources without failing Success Criterion 2.4.4 Link Purpose (In Context) (if said links are in separate documents or shadow trees)

Accessibility Support

There are no major accessibility support issues known for this rule.

Background

This rule is designed specifically for 2.4.4 Link Purpose (In Context), which requires the purpose to be clear within the context of a link. Because links that do not have this, also are not clear without that context, this rule maps to 2.4.9 Link Purpose (Link only) as well. In order to adequately test the expectation, some of the passed examples do not satisfy 2.4.9 Link Purpose (Link only).

This rule specifically targets links within the exact same context. Links with identical name that are in identical (but not the same) contexts also fail 2.4.4 Link Purpose (In Context). However, defining “identical context” unambiguously was not really possible and was left out of this rule.

Bibliography

Accessibility Requirements Mapping

2.4.4 Link Purpose (In Context) (Level A)
- Learn more about 2.4.4 Link Purpose (In Context)
- 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
2.4.9 Link Purpose (Link Only) (Level AAA)
- Learn more about 2.4.9 Link Purpose (Link Only)
- Required for conformance to WCAG 2.0 and later on level AAA.
- 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

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

Open in a new tab

These two HTML a elements have the same accessible name and context and link to the same resource.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">About us</a
		>) and get in touch (
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">About us</a>)
	</p>
</html>

Passed Example 2

Open in a new tab

These two HTML a elements have the same accessible name and context, and resolve to the same resource after an instant redirect.

<html lang="en">
	<div>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">About us</a
		>) and get in touch (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/redirect.html"
			>About us</a
		>)
	</div>
</html>

Passed Example 3

Open in a new tab

These two HTML a elements have the same accessible name and context, and resolve to identical resources.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">About us</a
		>) and get in touch (<a
			href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index-copy.html"
			>About us</a
		>)
	</p>
</html>

Passed Example 4

Open in a new tab

These two HTML a elements have the same accessible name and context, and resolve to pages that serve the same purpose because the content section is the same.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html"
			>Contact us</a
		>) and get in touch (
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/careers/contact.html">Contact us</a
		>)
	</p>
</html>

Passed Example 5

Open in a new tab

These two HTML a elements have the same accessible name and context, and go to pages that fulfill the same purpose in relation to the link because they contain the same relevant information.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html">Call us</a
		>) and get in touch (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page2.html"
			>Call us</a
		>)
	</p>
</html>

Passed Example 6

Open in a new tab

These two HTML a elements have the same accessible name and context, and go to pages that use different layouts but have the same purpose.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html"
			>Contact us</a
		>) and get in touch (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page3.html"
			>Contact us</a
		>)
	</p>
</html>

Passed Example 7

Open in a new tab

These two HTML span elements have an explicit role of link, the same accessible name, the same context, and link to the same resource.

<html lang="en">
	<p>
		<span
			role="link"
			tabindex="0"
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html'"
		>
			My university
		</span>

		<span
			role="link"
			tabindex="0"
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html'"
		>
			My university
		</span>
	</p>
</html>

Passed Example 8

Open in a new tab

These two SVG a and HTML a elements have the same accessible name, same context and link to the same resource.

<html lang="en">
	<p>
		<a href="https://act-rules.github.io/">ACT rules</a>

		<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
			<a href="https://act-rules.github.io/" aria-label="ACT rules">
				<circle cx="50" cy="40" r="35" />
			</a>
		</svg>
	</p>
</html>

Failed

Failed Example 1

Open in a new tab

These two HTML a elements have the same accessible name and context but go to different resources.

<html lang="en">
	<p>
		We are on social media:
		<a href="https://act-rules.github.io/">ACT rules</a>
		<a href="https://www.w3.org/community/act-r/">ACT rules</a>
	</p>
</html>

Failed Example 2

Open in a new tab

These two HTML a elements have the same accessible name and context. They link to web pages that are similar, but have different information in their content.

<html lang="en">
	<div>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html"
			>Contact us</a
		>) and get in touch (
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/admissions/contact.html"
			>Contact us</a
		>)
	</div>
</html>

Failed Example 3

Open in a new tab

These two HTML span elements have an explicit role of link, same accessible name and context, but link to resources that offer different content.

<html lang="en">
	<p>
		Learn more (<span
			role="link"
			tabindex="0"
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html'"
			>Contact us</span
		>) and get in touch (<span
			role="link"
			tabindex="0"
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/admissions/contact.html'"
			>Contact us</span
		>)
	</p>
</html>

Failed Example 4

Open in a new tab

These two SVG a elements have the same accessible name and context but link to different resources.

<html lang="en">
	<p>
		<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
			<a href="https://act-rules.github.io/" aria-label="ACT rules">
				<circle cx="50" cy="40" r="35" />
			</a>

			<a href="https://www.w3.org/community/act-r/">
				<text x="50" y="90" text-anchor="middle">
					ACT rules
				</text>
			</a>
		</svg>
	</p>
</html>

Failed Example 5

Open in a new tab

These two HTML a elements with the same accessible name and context resolve to the same resource after redirect, but the redirect is not instant.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html"
			>Contact us</a
		>) and get in touch (<a
			href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/redirect1.html"
			>Contact us</a
		>)
	</p>
</html>

Inapplicable

Inapplicable Example 1

Open in a new tab

These HTML a and area elements do not have a role of link.

<html lang="en">
	<a>Link text</a>
	<area aria-label="Link text" />
</html>

Inapplicable Example 2

Open in a new tab

These two HTML a elements have different accessible names.

Note: It is a best practice for Success Criterion 2.4.4: Link Purpose (In Context) that identical links have identical accessible names. This is however not a requirement.

<html lang="en">
	<p>
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html">Reach out</a>
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html">Contact us</a>
	</p>
</html>

Inapplicable Example 3

Open in a new tab

These two HTML a elements have the same accessible name and link to the same resource but different programmatically determined link contexts.

<html lang="en">
	<ul>
		<li>
			To learn more about us:
			<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a>
		</li>
		<li>
			To get in touch with us:
			<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a>
		</li>
	</ul>
</html>

Inapplicable Example 4

Open in a new tab

These two span elements do not have a semantic role of link.

<html lang="en">
	<p>
		Learn more (<span
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html'"
			>Contact Us </span
		>) and get in touch (<span
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page2.html'"
			>Contact Us </span
		>)
	</p>
</html>

Inapplicable Example 5

Open in a new tab

These two HTML a elements have the same accessible name and link to the same resource but different programmatically determined link contexts. Even if the contexts have identical content, they are not the same (the same elements).

<html lang="en">
	<div>
		You can learn more in the
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a> page.
	</div>
	<div>
		You can learn more in the
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a> page.
	</div>
</html>

Inapplicable Example 6

Open in a new tab

These two HTML a elements have the same accessible name but different programmatically determined link contexts because the div elements place them in different display blocks.

<div><a href="https://www.w3.org/WAI/">Read more</a> about the W3C WAI</div>
<div><a href="https://www.w3.org/International/">Read more</a> about the W3C internationalization</div>

Glossary

Accessible Name

The accessible name is the programmatically determined name of a user interface element that is included in the accessibility tree.

The accessible name is calculated using the accessible name and description computation.

For native markup languages, such as HTML and SVG, additional information on how to calculate the accessible name can be found in HTML Accessibility API Mappings 1.0, Accessible Name and Description Computation (working draft) and SVG Accessibility API Mappings, Name and Description (working draft).

For more details, see examples of accessible name.

Note: As per the accessible name and description computation, each element always has an accessible name. When no accessible name is provided, the element will nonetheless be assigned an empty ("") one.

Note: As per the accessible name and description computation, accessible names are flat string trimmed of leading and trailing whitespace. Notably, it is not possible for a non-empty accessible name to be composed only of whitespace since these must be trimmed.

Equivalent resource

Non-identical resources can still be equivalent resources by equally complying to the expectation formed by the user when navigating to them, thus serving an equivalent purpose. This would usually involve that the advertised key content is the same.

Web pages and documents (e.g. PDFs, office formats etc.) may be equivalent resources, even if the resources:

are located on different URLs, including different domains
present different navigation options, e.g. through bread crumbs or local sub menus
contain different amounts of information and/or differently worded information
use different layouts.

If all resources cover the user’s expectations equally well, the resources are considered to be equivalent.

Note: The user’s expectations for the resource can be formed by different things, e.g. the name of the link leading to the resource, with or without the context around the link. This depends on the accessibility requirement that is tested.

Note: If the same content is presented in different formats or languages, the format or language itself is often part of the purpose of the content, e.g. an article as both HTML and PDF, an image in different sizes, or an article in two different languages. If getting the same content in different formats or languages is the purpose of having separate links, the resources are not equivalent.

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

An element is focusable if one or both of the following are true:

the element is part of sequential focus navigation; or
the element has a tabindex value that is not null.

Exception: Elements that lose focus during a period of up to 1 second after gaining focus, without the user interacting with the page the element is on, are not considered focusable.

Notes:

The 1 second time span is an arbitrary limit which is not included in WCAG. Given that scripts can manage the focus state of elements, testing the focusability of an element consistently would be impractical without a time limit.
The tabindex value of an element is the value of the tabindex attribute parsed using the rules for parsing integers. For the tabindex value to be different from null, it needs to be parsed without errors.

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 are exposed to assistive technologies. This allows users of assistive technology to access the elements in a way that meets 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.

Programmatically hidden elements are removed from the accessibility tree. However, some browsers will leave focusable elements with an aria-hidden attribute set to true in the accessibility tree. Because they are hidden, these elements are considered not included in the accessibility tree. This may cause confusion for users of assistive technologies because they may still be able to interact with these focusable elements using sequential keyboard navigation, even though the element should not be included in the accessibility tree.

Inheriting Semantic Role

An element with an inheriting semantic role of X is any element with a non-abstract semantic role that inherits from X, or is the same as X.

Example: An “inheriting semantic link” is any element that either has the semantic role of link or a semantic role that inherits from the link role, such as doc-biblioref.

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 they are programmatically hidden. This is different from marking the element as decorative and does not convey the same intention. Notably, being programmatically hidden 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.

Matching characters

A sequence of characters is considered to match another if, after removing leading and trailing space characters and replacing remaining occurrences of one or more space characters with a single space, the two sequences of characters are equal character-by-character, ignoring any differences in letter casing.

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.

Programmatically Determined Link Context

The programmatically determined context of a link (or programmatically determined link context) is the set of all elements that are included in the accessibility tree, and have one or more of the following relationships to the link:

being an ancestor of the link in the flat tree with a semantic role of listitem; or
being the closest ancestor of the link in the flat tree that generates a block container; or
being the closest ancestor of the link in the flat tree that has a semantic role of cell or gridcell; or
being a header cell assigned to the closest ancestor of the link in the flat tree that has a semantic role of cell or gridcell; or
being referenced by an aria-describedby attribute of the link.

This definition is based on the WCAG definition of programmatically determined link context.

This definition assumes that the HTML document with the link is a document using HTML according to the specification.

Programmatically Hidden

An HTML element is programmatically hidden if either it has a computed CSS property visibility whose value is not visible; or at least one of the following is true for any of its inclusive ancestors in the flat tree:

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

Note: Contrary to the other conditions, the visibility CSS property may be reverted by descendants.

Note: The HTML standard suggests setting the CSS display property to none for elements with the hidden attribute. While not required by HTML, all modern browsers follow this suggestion. Because of this the hidden attribute is not used in this definition. In browsers that use this suggestion, overriding the CSS display property can reveal elements with the hidden attribute.

Same resource

Two or more resources can be the same resource even though the URLs for them are different. This can be due to URL parsing, server settings, redirects and DNS aliasing.

If the parsed URLs for two resources are identical, the resources are the same resource.

Depending on the server, URLs can either be case-sensitive or case-insensitive, meaning that <a href="page1.html"> and <a href="Page1.html"> lead to either the same or two different pages.

Fully parsed URLs can be different, but still lead to the same resource after making the HTTP request, due to redirects and DNS aliasing. For example, these URLs are all fully normalized: http://example.com/, http://www.example.com/, https://www.example.com/. The server can however be configured to serve the same site for http and https, and the same site for example.com and www.example.com. This is common, but not guaranteed.

Some types of redirects are also caused by user agents, e.g. ensuring that http://example.com/ and http://example.com resolve to the same resource.

On the other hand, identical relative URLs do not necessarily resolve to the same resource, even if they are in the same web page (HTML). This happen because external content can be included through iframe and URLs in or out of it will resolve relatively to different base URLs.

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 it is not programmatically hidden, 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.

This definition can be used in expressions such as “semantic button” meaning any element with a semantic role of button.

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.

Web page (HTML)

An HTML web page is the set of all fully active documents which share the same top-level browsing context.

Note: Nesting of browsing context mostly happens with iframe and object. Thus a web page will most of the time be a “top-level” document and all its iframe and object (recursively).

Note: Web pages as defined by WCAG are not restricted to the HTML technology but can also include, e.g., PDF or DOCX documents.

Note: Although web pages as defined here are sets of documents (and do not contain other kind of nodes), one can abusively write that any node is “in a web page” if it is a shadow-including descendant of a document that is part of that web page.

Rule Versions

This is the first version of this ACT rule.

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.