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"ARIA required context role" (ff89c9): resolve TF feedback #1554

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Jun 17, 2021
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"ARIA required context role" (ff89c9): resolve TF feedback #1554

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Inline def of owned elements
Jym77 Mar 11, 2021
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Merge branch 'develop' into aria-required-context-role-tf-review
Jym77 Apr 8, 2021
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Jym77 Apr 22, 2021
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Merge branch 'develop' into aria-required-context-role-tf-review
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Jym77 Jun 17, 2021
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30 changes: 16 additions & 14 deletions _rules/aria-required-context-role-ff89c9.md
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Expand Up @@ -29,15 +29,15 @@ This rule applies to any HTML or SVG element that is [included in the accessibil

## 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.
Each test target is the child in the [accessibility tree][] of 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](https://www.w3.org/TR/WCAG21/#info-and-relationships).

## Accessibility Support

- User agents do not all have the same accessibility tree. Particularly the method of deriving which element [owns][owned by] which other elements varies between browsers. This can lead to different results for this rule, depending on which accessibility tree is used as input.
- User agents do not all have the same accessibility tree. 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][implicit role] and [explicit][explicit role] roles.

Expand All @@ -47,7 +47,9 @@ The applicability of this rule is limited to the [WAI-ARIA 1.1 Recommendation][a

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](https://www.w3.org/TR/wai-aria-1.1/#dfn-owned-element). In this rule "owned by" includes only direct children of the owner element, whereas an "owned element" is any descendant of the owner.
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 rule is restricted to direct parent-child relation in the [accessibility tree][] which is more strict than the definition of ["owned element" in WAI-ARIA](https://www.w3.org/TR/wai-aria-1.1/#dfn-owned-element). This rule mimics, on the roles level, the [content model](https://html.spec.whatwg.org/#concept-element-content-model) of HTML.
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Shouldn't we delete the sentence where we are saying that this rule mimics the HTML content model? Asking because the definition of the content model is suggesting that it's both children and descendants of the element/ test target.

It's contradictory to the beginning of the paragraph where we insist that this rule is restricted to direct parent-child relation.

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I agree with Aron's suggestion

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I can go either way on this.

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Actually, it depends where we look 🤯
The link used here indeed says

A normative description of what content must be included as children and descendants of the element.

but a couple of line below we have 3.2.5 Content models stating

Each element defined in this specification has a content model: a description of the element's expected contents. An HTML element must have contents that match the requirements described in the element's content model. The contents of an element are its children in the DOM.

🤷

As far as I remember, HTML content model only refers to children, not further descendants (despite what the def says).

Additionally, the idea is not just to consider a single level in the tree (e.g., the rule allows the table > rowgroup > row chain which is 2 levels) but more than the chain have to be considered between parent/children and not ancestors/descendant.

Using the ARIA def of "owned element", something like table > rowgroup > navigation > row would be allowed because the row is "owned by" the rowgroup (as a descendant) but is not a "child in the accessiblity tree".

So the difference is not about only looking at children, but about looking one step at a time and not skipping any.

The reason why we do this stepwise checks (disregarding ARIA specs) is that the content model is doing likewise. That is <table><tbody><nav><tr> is not OK because <nav> is not allowed in a <tbody>. The content model is only looking one step at a time, and individual elements' content model only mention children, but builds up a model that restrict descendants further away.

Essentially, performing the same checks on implicit roles (only) should flag violations of the content model (not all of them, but some of them).

So, this is what I was trying to say there…

  • We stray away from ARIA def.
  • We do so because we take inspiration from content model.

I'm afraid that keeping only the first part (the action) without the second (its justification) could lead to much confusion ("why are you not following ARIA specs?")

Not sure how to rephrase it to convey that information… I'll let it simmer a bit in case any of you has a brillant idea 😁
Easy fix might just be to switch the link and use the other one that does not mention descendants…

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I understand, and agre, with your reasoning.
Unfortunately, I don't have a better idea than what you suggested (i.e. change the link target).


[Subclass roles][subclass role] of [required context roles][] are not automatically included as possible [required context roles][]. For example, the [`feed`](https://www.w3.org/TR/wai-aria-1.1/#feed) role is not a possible [required context role][] for [`listitem`](https://www.w3.org/TR/wai-aria-1.1/#listitem), even though [`feed`](https://www.w3.org/TR/wai-aria-1.1/#feed) is a [subclass role][] of the [`list`](https://www.w3.org/TR/wai-aria-1.1/#list) role.

Expand All @@ -62,7 +64,7 @@ Some user agents try to correct missing [required context roles][] or incorrect

#### Passed Example 1

These elements with an [explicit role][] of `listitem` are [owned by][] an element with their [required context role][], `list`, expressed as an [explicit role][].
These elements with an [explicit role][] of `listitem` are children in the [accessibility tree][] of an element with their [required context role][], `list`, expressed as an [explicit role][].

```html
<div role="list">
Expand All @@ -73,7 +75,7 @@ These elements with an [explicit role][] of `listitem` are [owned by][] an eleme

#### Passed Example 2

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][sc411] because the [`ul` element][ul] does not respect its [content model][].
These elements with an [explicit role][] of `listitem` are children in the [accessibility tree][] of 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][sc411] because the [`ul` element][ul] does not respect its [content model][].

```html
<ul>
Expand All @@ -84,7 +86,7 @@ These elements with an [explicit role][] of `listitem` are [owned by][] an eleme

#### Passed Example 3

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][owned by] "skips" through presentational nodes because they are not [included in the accessibility tree][].
These elements with an [explicit role][] of `listitem` are children in the [accessibility tree][] of an element with their [required context role][] even though they are not its children in DOM. The presentational node is not [included in the accessibility tree][].

```html
<div role="list">
Expand All @@ -97,7 +99,7 @@ These elements with an [explicit role][] of `listitem` are [owned by][] an eleme

#### Passed Example 4

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](https://www.w3.org/TR/wai-aria-1.1/#scope).
These elements with an [explicit role][] of `listitem` are children in the [accessibility tree][] of an element with their [required context role][] even though they are not its DOM descendants. The `aria-owns` attribute is used to alter the accessibility tree and place the target elements in their [required context role](https://www.w3.org/TR/wai-aria-1.1/#scope).

```html
<div role="list" aria-owns="item1 item2"></div>
Expand All @@ -107,7 +109,7 @@ These elements with an [explicit role][] of `listitem` are [owned by][] an eleme

#### Passed Example 5

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](https://www.w3.org/TR/wai-aria-1.1/#scope).
These elements with an [explicit role][] of `listitem` are children in the [accessibility tree][] of an element with their [required context role][] even though they are not its DOM children. The `aria-owns` attribute is used to alter the accessibility tree and place the target elements in their [required context role](https://www.w3.org/TR/wai-aria-1.1/#scope).

```html
<div role="list" aria-owns="item1 item2">
Expand All @@ -120,7 +122,7 @@ These elements with an [explicit role][] of `listitem` are [owned by][] an eleme

#### Passed Example 6

These elements with an [explicit role][] of `listitem` are [owned by][] an element with their [required context role][] because implicit [ownership][owned by] (inherited from DOM tree structure) crosses shadow boundaries.
These elements with an [explicit role][] of `listitem` are children in the [accessibility tree][] of an element with their [required context role][] because the [accessibility tree][] mimics the DOM tree across shadow boundaries.

```html
<div id="host" role="list"></div>
Expand All @@ -136,15 +138,15 @@ These elements with an [explicit role][] of `listitem` are [owned by][] an eleme

#### Failed Example 1

This element with an [explicit role][] of `listitem` is not [owned by][] an element with its [required context role][].
This element with an [explicit role][] of `listitem` is not a child in the [accessibility tree][] of an element with its [required context role][].

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

#### Failed Example 2

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.
These elements with an [explicit role][] of `listitem` are not children in the [accessibility tree][] of an element with their [required context role][], but of an element with the `tabpanel` role.

```html
<div role="list">
Expand All @@ -157,7 +159,7 @@ These elements with an [explicit role][] of `listitem` are not [owned by][] an e

#### Failed Example 3

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][].
These elements with an [explicit role][] of `listitem` are not children in the [accessibility tree][] of an element with their [required context role][]. They are instead children in the [accessibility tree][] of 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][].

```html
<div role="list">
Expand All @@ -170,7 +172,7 @@ These elements with an [explicit role][] of `listitem` are not [owned by][] an e

#### Failed Example 4

These elements with an [explicit role][] of `listitem` are not [owned by][] an element with their [required context role][] because explicit [ownership][owned by] (set by `aria-owns`) does not cross shadow boundaries.
These elements with an [explicit role][] of `listitem` are not children in the [accessibility tree][] of an element with their [required context role][] because explicit parent-child relation in the [accessibility tree][] (set by `aria-owns`) does not cross shadow boundaries.

```html
<div role="list" aria-owns="item1 item2"></div>
Expand Down Expand Up @@ -233,6 +235,7 @@ There is no element with an [explicit role][] different from its [implicit role]
</ul>
```

[accessibility tree]: https://www.w3.org/TR/act-rules-aspects/#input-aspects-accessibility 'Definition of accessibility tree'
[aria 1.1]: https://www.w3.org/TR/wai-aria-1.1/ 'WAI ARIA 1.1 specifications'
[content model]: https://html.spec.whatwg.org/multipage/dom.html#concept-element-content-model 'HTML definition of the Content Model'
[dpub 1.0]: https://www.w3.org/TR/dpub-aria-1.0/ 'Digital Publishing WAI-ARIA Module (DPUB ARIA) 1.0'
Expand All @@ -242,7 +245,6 @@ There is no element with an [explicit role][] different from its [implicit role]
[implicit role]: #implicit-role 'Definition of Implicit Role'
[implicit semantic role]: #implicit-role 'Definition of Implicit Role'
[included in the accessibility tree]: #included-in-the-accessibility-tree 'Definition of Included in the Accessibility Tree'
[owned by]: #owned-by 'Definition of Owned by'
[required context role]: https://www.w3.org/TR/wai-aria-1.1/#scope 'WAI ARIA definition of Required Context Role'
[required context roles]: https://www.w3.org/TR/wai-aria-1.1/#scope 'WAI ARIA definition of Required Context Role'
[sc411]: https://www.w3.org/TR/WCAG21/#parsing 'Success Criterion 4.1.1 Parsing'
Expand Down