Add definition for implicit/explicit ARIA attributes

_rules/aria-state-or-property-permitted-5c01ea.md

@@ -36,7 +36,7 @@ acknowledgments:
 
 ## Applicability
 
-This rule applies to any [WAI-ARIA state or property][] that is specified on an [HTML or SVG element][namespaced element] that is [included in the accessibility tree][].
+This rule applies to any [WAI-ARIA state or property][] that is [explicitly set][aria set explicit] on an [HTML or SVG element][namespaced element] that is [included in the accessibility tree][].
 
 ## Expectation 1
 
@@ -64,6 +64,8 @@ The presence of prohibited ARIA attributes is often the result of a developer us
 
 In HTML, there are language features that do not have corresponding implicit WAI-ARIA semantics. As per [ARIA in HTML](https://www.w3.org/TR/html-aria/), those elements can have [global states or properties][global]. Some of those elements can also have [inherited][], [supported][], or [required][] [states][state] or [properties][property] that correspond to a [WAI-ARIA role](https://www.w3.org/TR/wai-aria-1.2/#introroles). For example, the `audio` element has no corresponding ARIA semantics but it can have [inherited][], [supported][], or [required][] [states][state] or [properties][property] of the [`application` role](https://www.w3.org/TR/wai-aria-1.2/#application).
 
+This rule only applies to [explicitly set][aria set explicit] attributes since these have been provided by authors and using the wrong one is therefore an author issue. If an [implicitly set][aria set implicit] attribute is incorrect, this is not necessarily an author error, e.g., it can be the result of re-purposing an existing element.
+
 Assessing the value of the attribute is out of scope for this rule.
 
 ### Related rules
@@ -173,6 +175,14 @@ This `input` element does not have an [explicit role][] of `textbox`, but the `a
 <label>Password<input type="password" aria-required="true"/></label>
 ```
 
+#### Passed Example 12
+
+This `button` has an [implicitly set][aria set implicit] `aria-checked` state since it uses an `input` element with a `type` [attribute value][] of `checkbox`.
+
+```html
+<input type="checkbox" role="button" />
+```
+
 ### Failed
 
 #### Failed Example 1
@@ -217,6 +227,8 @@ This `div` element is not [included in the accessibility tree][], hence its [WAI
 <div role="button" aria-sort="" style="display:none;"></div>
 ```
 
+[aria set explicit]: #aria-attribute-set:explicit 'Definition of ARIA Attribute Set Explicitly'
+[aria set implicit]: #aria-attribute-set:implicit 'Definition of ARIA Attribute Set Implicitly'
 [attribute value]: #attribute-value 'Definition of attribute value'
 [explicit role]: #explicit-role 'Definition of Explicit Role'
 [focusable]: #focusable 'Definition of focusable'

_rules/role-required-states-and-properties-4e8ab6.md

@@ -31,11 +31,13 @@ acknowledgments:
 
 ## Applicability
 
-This rule applies to any [HTML or SVG element][] that is [included in the accessibility tree][] and has an [explicit semantic role][], except if the element has an [implicit semantic role][] that is identical to the [explicit semantic role][].
+This rule applies to any [HTML or SVG element][] that is [included in the accessibility tree][].
 
 ## Expectation
 
-For each test target, the [WAI-ARIA required states and properties][] for the role are set and not empty (`""`), unless the state or property has a default value listed under [WAI-ARIA implicit value for role][].
+For each test target, the [WAI-ARIA required states and properties][] for the role are [set][aria set] and not empty (`""`).
+
+The attributes may be [explicitly set][aria set explicit], [implicitly set][aria set implicit], or [set by default][aria set default].
 
 ## Assumptions
 
@@ -51,7 +53,7 @@ This rule relies on browsers and assistive technologies to support leaving out [
 
 Omitting [WAI-ARIA required states and properties][] is often the result of a developer error. When required properties are missing and a default value is not specified by [WAI-ARIA Specifications][], the behavior is not defined. For [WAI-ARIA 1.2][], the only [explicit semantic roles][explicit semantic role] with a required property with a default value are the `option` and `tabs roles` for the `aria-selected` property.
 
-This rule is testing author built components that specify [explicit semantic roles][explicit semantic role] and not components that keep their [implicit semantic role][]. For components that keep their [implicit semantic role][], all native HTML and SVG elements have native attributes that are mapped to all of the [WAI-ARIA required states and properties](https://www.w3.org/TR/wai-aria/#requiredState). Most of these mappings are defined in the [HTML Accessibility API Mappings, Attribute State and Property Mappings][html aam].
+The way the attribute is [set][aria set] doesn't matter for this rule. As long as authors can rely on User Agents or Assistive Technologies to set the attribute, this won't create problems for users. As per the [First Rule of ARIA use][], authors should rely on [implicitly set][aria set implicit] attributes when possible.
 
 ### Bibliography
 
@@ -126,6 +128,28 @@ This `combobox` has the required properties `aria-controls` and `aria-expanded`.
 </ul>
 ```
 
+#### Passed Example 7
+
+This `checkbox` has its required `aria-checked` property [implicitly set][aria set implicit].
+
+```html
+<label>
+	<input type="checkbox" />
+	Check me
+</label>
+```
+
+#### Passed Example 8
+
+This `menuitemcheckbox` has its required `aria-checked` property [implicitly set][aria set implicit].
+
+```html
+<label>
+	<input type="checkbox" role="menuitemcheckbox" />
+	Check me
+</label>
+```
+
 ### Failed
 
 #### Failed Example 1
@@ -205,23 +229,18 @@ This `div` does not have a [semantic role](#semantic-role).
 
 #### Inapplicable Example 2
 
-This `checkbox` has an [implicit semantic role](#implicit-role) that is identical to the [explicit semantic role](#explicit-role). This allows native HTML `checked` attribute to apply.
-
-```html
-<input type="checkbox" role="checkbox" />
-```
-
-#### Inapplicable Example 3
-
 This `combobox` is not [included in the accessibility tree][] due to its styling, hiding it from everybody.
 
 ```html
 <div role="combobox" style="display:none;"></div>
 ```
 
+[aria set]: #aria-attribute-set 'Definition of ARIA Attribute Set'
+[aria set default]: #aria-attribute-set:default 'Definition of ARIA Attribute Set by Default'
+[aria set explicit]: #aria-attribute-set:explicit 'Definition of ARIA Attribute Set Explicitly'
+[aria set implicit]: #aria-attribute-set:implicit 'Definition of ARIA Attribute Set Implicitly'
 [explicit semantic role]: #explicit-role 'Definition of explicit semantic role'
-[html aam]: https://www.w3.org/TR/html-aam-1.0/#html-attribute-state-and-property-mappings 'Specification of HTML attributes value mapping to ARIA states and properties'
-[implicit semantic role]: #implicit-role 'Definition of implicit semantic role'
+[first rule of aria use]: https://www.w3.org/TR/using-aria/#rule1 'First Rule of ARIA Use'
 [included in the accessibility tree]: #included-in-the-accessibility-tree 'Definition of Included in The Accessibility Tree'
 [wai-aria required states and properties]: https://www.w3.org/TR/wai-aria-1.2/#requiredState
 [wai-aria specifications]: #wai-aria-specifications 'Definition of WAI-ARIA Specifications'

pages/glossary/aria-attribute-set.md

@@ -0,0 +1,30 @@
+---
+title: ARIA state or property is set
+key: aria-attribute-set
+unambiguous: true
+objective: true
+input_aspects:
+  - Accessibility tree
+  - CSS styling
+  - DOM tree
+---
+
+An ARIA [state][aria state] or [property][aria property] is <dfn>set</dfn> on an [HTML element][namespaced element] when it has a value. This may happen in three ways:
+
+- It is <dfn id="aria-attribute-set:explicit">explicitly set</dfn> if there is a corresponding `aria-*` HTML attribute on the element, whose value is valid for this ARIA [state][aria state] or [property][aria property].
+
+  For example, `aria-label` is explicitly set on `<button aria-label="Next page">Next</button>`.
+
+- It is <dfn id="aria-attribute-set:implicit">implicitly set</dfn> if there is no corresponding `aria-*` HTML attribute on the element, but the element has an [implicit semantic role][implicit role] that has a value for this ARIA [state][aria state] or [property][aria property] defined in [HTML Attribute State and Property Mappings][aria attribute mapping].
+
+  For example, `aria-checked` is implicitly set on `<input type="checkbox" checked />`.
+
+- It is <dfn id="aria-attribute-set:default">set by default</dfn> if there is no corresponding `aria-*` HTML attribute on the element, and the element has an [implicit semantic role][implicit role] that has a default value for this ARIA [state][aria state] or [property][aria property].
+
+  For example, `aria-expanded` is set by default on `<details><summary>Details</summary></details>`.
+
+[aria attribute mapping]: https://www.w3.org/TR/html-aam-1.0/#html-attribute-state-and-property-mappings 'HTML Attribute State and Property Mappings'
+[aria property]: https://www.w3.org/TR/wai-aria-1.2/#dfn-property 'Definition of ARIA Property'
+[aria state]: https://www.w3.org/TR/wai-aria-1.2/#dfn-state 'Definition of ARIA State'
+[implicit role]: #implicit-role 'Definition of Implicit Semantic Role'
+[namespaced element]: #namespaced-element 'Definition of Namespaced Element'