diff --git a/_rules/aria-state-or-property-permitted-5c01ea.md b/_rules/aria-state-or-property-permitted-5c01ea.md
index bd68a9ea7e9..f70d20eded1 100755
--- a/_rules/aria-state-or-property-permitted-5c01ea.md
+++ b/_rules/aria-state-or-property-permitted-5c01ea.md
@@ -37,7 +37,7 @@ 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
 
@@ -55,6 +55,8 @@ In HTML, there are language features that do not have corresponding implicit WAI
 
 Note that required WAI-ARIA states or properties for a role may change with the advance of the WAI-ARIA specifications. For example, both aria-expanded and aria-controls were required in [ARIA 1.2](https://www.w3.org/TR/wai-aria-1.2/#combobox) for combobox role, but the aria-controls was removed from required states or properties in [ARIA 1.3](https://www.w3.org/TR/wai-aria-1.3/#combobox). The examples in this rule follow [ARIA 1.3](https://www.w3.org/TR/wai-aria-1.3/#combobox).
 
+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.
 
 ### Assumptions
@@ -237,7 +239,18 @@ This `div` element is not [included in the accessibility tree][], hence its [WAI
 <div role="button" aria-sort="" style="display:none;"></div>
 ```
 
+#### Inapplicable Example 3
+
+This `button` does not have any [explicitly set][aria set explicit] ARIA attribute. It has an [implicitly set][aria set implicit] `aria-checked` state, due to the [absence of a `checked` attribute][checked absent] on the `input` element with a `type` [attribute value][] of `checkbox`.
+
+```html
+<input type="checkbox" role="button" />
+```
+
+[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'
+[checked absent]: https://www.w3.org/TR/html-aam-1.0/#att-checked-absent 'HTML Accessibility API Mappings, Attribute Checked absent'
 [explicit role]: #explicit-role 'Definition of Explicit Role'
 [focusable]: #focusable 'Definition of focusable'
 [global]: https://www.w3.org/TR/wai-aria-1.2/#global_states 'Definition of Global ARIA States and Properties'
diff --git a/_rules/role-attribute-valid-value-674b10.md b/_rules/role-attribute-valid-value-674b10.md
index ec2d9ea3f18..889ae5d85d2 100755
--- a/_rules/role-attribute-valid-value-674b10.md
+++ b/_rules/role-attribute-valid-value-674b10.md
@@ -49,6 +49,8 @@ The `role` attribute is a set of [space separated tokens][]. Having a [whitespac
 
 Not every role can be used on every element. Which ARIA roles may be used on which HTML elements is defined in [ARIA in HTML](https://www.w3.org/TR/html-aria/). Testing this is not part of this rule.
 
+This rule considers the [value of the attribute as set in the HTML code][html attribute value], which differs from the [attribute value][attribute value] obtained after parsing it and discarding invalid tokens.
+
 ### Assumptions
 
 There are no assumptions.
@@ -167,7 +169,7 @@ This `role` attribute is empty ("").
 This `role` attribute is only [ASCII whitespace][].
 
 ```html
-<input type="text" role=" " aria-label="field name"/>
+<input type="text" role=" " aria-label="field name" />
 ```
 
 #### Inapplicable Example 5
@@ -179,7 +181,9 @@ This `role` attribute is specified on an element which is [programmatically hidd
 ```
 
 [ascii whitespace]: https://infra.spec.whatwg.org/#ascii-whitespace 'Definition of ASCII whitespace'
+[attribute value]: #attribute-value:role 'Definition of Attribute Value of the Role Attribute'
 [html or svg element]: #namespaced-element
+[html attribute value]: https://html.spec.whatwg.org/multipage/dom.html#attributes 'HTML Specification of Attribute Value'
 [implicit role]: #implicit-role 'Definition of Implicit Role'
 [programmatically hidden]: #programmatically-hidden 'Definition of Programmatically Hidden'
 [role attribute]: https://www.w3.org/TR/role-attribute/ 'Specification of the Role attribute'
diff --git a/_rules/role-required-states-and-properties-4e8ab6.md b/_rules/role-required-states-and-properties-4e8ab6.md
index 425a9800d6a..aa1a06be1b2 100755
--- a/_rules/role-required-states-and-properties-4e8ab6.md
+++ b/_rules/role-required-states-and-properties-4e8ab6.md
@@ -33,17 +33,19 @@ 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].
 
 ## Background
 
 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.
 
 ### Assumptions
 
@@ -67,7 +69,7 @@ This rule relies on browsers and assistive technologies to support leaving out [
 
 #### Passed Example 1
 
-This `heading` has the required `aria-level` property.
+This `heading` has the required `aria-level` property [explicitly set][aria set explicit].
 
 ```html
 <div role="heading" aria-level="1">
@@ -77,7 +79,7 @@ This `heading` has the required `aria-level` property.
 
 #### Passed Example 2
 
-This `checkbox` has the required `aria-checked` property.
+This `checkbox` has the required `aria-checked` property [explicitly set][aria set explicit].
 
 ```html
 <div role="checkbox" aria-checked="false" aria-labelledby="label"></div>
@@ -86,7 +88,7 @@ This `checkbox` has the required `aria-checked` property.
 
 #### Passed Example 3
 
-This `scrollbar` has the required properties `aria-controls` and `aria-valuenow`. `aria-valuemin` has a default value of 0 and `aria-valuemax` of 100.
+This `scrollbar` has the required properties `aria-controls` and `aria-valuenow` [explicitly set][aria set explicit]. `aria-valuemin` has a default value of 0 and `aria-valuemax` of 100 and are thus [set by default][aria set default].
 
 ```html
 <div role="scrollbar" aria-controls="content" aria-valuenow="0"></div>
@@ -95,7 +97,7 @@ This `scrollbar` has the required properties `aria-controls` and `aria-valuenow`
 
 #### Passed Example 4
 
-These `option` nodes do not need the required `aria-selected` property because it has a default value of `false`.
+These `option` nodes have the required `aria-selected` property [set by default][aria set default].
 
 ```html
 <div id="label">Tags</div>
@@ -107,7 +109,7 @@ These `option` nodes do not need the required `aria-selected` property because i
 
 #### Passed Example 5
 
-This `separator` is not a `widget` because it is not [focusable][]. The `separator` role only requires the `aria-valuenow` property when the element is focusable.
+This `separator` is not a `widget` because it is not [focusable][]. The `separator` role does not have any required property when the element is not focusable.
 
 ```html
 <p>My first HTML</p>
@@ -117,22 +119,52 @@ This `separator` is not a `widget` because it is not [focusable][]. The `separat
 
 #### Passed Example 6
 
-This `combobox` has the required properties `aria-controls` and `aria-expanded`.
+This `combobox` has the required properties `aria-controls` and `aria-expanded` [explicitly set][aria set explicit].
 
 ```html
 <label for="tag_combo" id="tag_label">Tag</label>
-<input type="text" id="tag_combo" role="combobox" aria-expanded="true" aria-controls="popup_listbox"/>
+<input type="text" id="tag_combo" role="combobox" aria-expanded="true" aria-controls="popup_listbox" />
 <ul role="listbox" id="popup_listbox" aria-labelledby="tag_label">
 	<li role="option">Zebra</li>
 	<li role="option" id="selected_option">Zoom</li>
 </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>
+```
+
+#### Passed Example 9
+
+This `iframe` element is [included in the accessibility tree][], even without a role, and therefore has no [WAI-ARIA required states and properties][].
+
+```html
+<iframe srcdoc="<div>ACT rules are awesome!</div>" title="ACT rules" />
+```
+
 ### Failed
 
 #### Failed Example 1
 
-This `heading` does not have the required `aria-level` property. Prior to [WAI-ARIA 1.2][] the `heading` role had an implicit default `aria-level` value of `2`. As of WAI-ARIA 1.2 this property must be explicitly set.
+This `heading` does not have the required `aria-level` property. Prior to [WAI-ARIA 1.2][] the `heading` role had a default `aria-level` value of `2`. As of WAI-ARIA 1.2 this property must be [explicitly set][aria set explicit].
 
 ```html
 <div role="heading">
@@ -142,7 +174,7 @@ This `heading` does not have the required `aria-level` property. Prior to [WAI-A
 
 #### Failed Example 2
 
-This `switch` does not have the required `aria-checked` property. Prior to [WAI-ARIA 1.2][] the `switch` role had an implicit default `aria-checked` value of `false`. As of WAI-ARIA 1.2 this property must be explicitly set.
+This `switch` does not have the required `aria-checked` property. Prior to [WAI-ARIA 1.2][] the `switch` role had a default `aria-checked` value of `false`. As of WAI-ARIA 1.2 this property must be [explicitly set][aria set explicit].
 
 ```html
 <div role="switch">
@@ -152,7 +184,7 @@ This `switch` does not have the required `aria-checked` property. Prior to [WAI-
 
 #### Failed Example 3
 
-This `checkbox` does not have the required property `aria-checked`. Prior to [WAI-ARIA 1.2][] the `checkbox` had an implicit default `aria-checked` value of `false`. As of WAI-ARIA 1.2 this property must be explicitly set.
+This `checkbox` does not have the required property `aria-checked`. Prior to [WAI-ARIA 1.2][] the `checkbox` role had a default `aria-checked` value of `false`. As of WAI-ARIA 1.2 this property must be [explicitly set][aria set explicit].
 
 ```html
 <div role="checkbox" aria-labelledby="label"></div>
@@ -171,7 +203,7 @@ This `separator` does not have the required `aria-valuenow` property. This is re
 
 #### Failed Example 5
 
-This `combobox` does not have the required `aria-expanded` property. Prior to [WAI-ARIA 1.2][] the `combobox` had an implicit default `aria-expanded` value of `false`. As of WAI-ARIA 1.2 this property must be explicitly set.
+This `combobox` does not have the required `aria-expanded` property. Prior to [WAI-ARIA 1.2][] the `combobox` had a default `aria-expanded` value of `false`. As of WAI-ARIA 1.2 this property must be [explicitly set][aria set explicit].
 
 ```html
 <label for="tag_combo">Tag</label>
@@ -186,7 +218,7 @@ This `combobox` does not have the required `aria-expanded` property. Prior to [W
 
 #### Inapplicable Example 1
 
-This `div` does not have a [semantic role](#semantic-role).
+This `div` is not [included in the accessibility tree][] due to its role of `generic`.
 
 ```html
 <div>Some Content</div>
@@ -194,23 +226,18 @@ 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" aria-label="Checkbox name"/>
-```
-
-#### 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'
diff --git a/pages/glossary/aria-attribute-set.md b/pages/glossary/aria-attribute-set.md
new file mode 100644
index 00000000000..2fa80f993a1
--- /dev/null
+++ b/pages/glossary/aria-attribute-set.md
@@ -0,0 +1,40 @@
+---
+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. If the [value][html attribute value] written in the HTML code is not valid for this ARIA [state][aria state] or [property][aria property] then the attribute is set but does not have an [attribute value][].
+
+  For example, `aria-label` is explicitly set on `<button aria-label="Next page">Next</button>`; and `aria-checked` is explicitly set on `<input type="checkbox" aria-checked="yes" />`, even though it does not have an [attribute value][].
+
+- 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 or one of its HTML attributes has an [ARIA attribute mapping][aria attribute mapping] setting this ARIA attribute.
+
+  For example, `aria-checked` is implicitly set both on `<input type="checkbox" checked />` (through the [presence of the HTML attribute `checked`][checked present]) and `<input type="checkbox" />` (through its [absence][checked absent]). It is not set on `<input type="text" />` given that the mapping for `checked` doesn't apply when the `input` element is not of type `checkbox` or `radio`.
+
+- It is <dfn id="aria-attribute-set:default">set by default</dfn> if there is no corresponding `aria-*` HTML attribute on the element, and either the element has a [semantic role][] that has a default value for this ARIA [state][aria state] or [property][aria property] or the attribute itself has a default value.
+
+  For example, `aria-haspopup` is set by default on `<div role="combobox"></div>` through the role of `combobox`.
+
+#### Background for ARIA attribute set
+
+For explicitly set attributes, this definition only looks at the value written in the HTML code, without considering its validity. Attributes that are explicitly set with an invalid value are author errors that are detected by the rule [Role attribute has valid value](https://www.w3.org/WAI/standards-guidelines/act/rules/674b10/), and authors should not rely on invalid value to have forbidden attributes discarded from roles not allowing it.
+
+For attributes set by default, this definition doesn't consider whether the attribute is allowed on the element (or role). Thus, `aria-expanded` (whose default value is `false`) is considered as set by default on `<input />` even though it is not allowed on the `textbox` role. While authors can (and should) rely on attributes to be set by default, they also have no direct control on them and therefore whether they are allowed on an element never causes an author error.
+
+[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'
+[attribute value]: #attribute-value 'Definition of Attribute Value'
+[checked absent]: https://www.w3.org/TR/html-aam-1.0/#att-checked-absent 'HTML Accessibility API Mappings, Attribute Checked absent'
+[checked present]: https://www.w3.org/TR/html-aam-1.0/#att-checked 'HTML Accessibility API Mappings, Attribute Checked present'
+[html attribute value]: https://html.spec.whatwg.org/multipage/dom.html#attributes 'HTML Specification of Attribute Value'
+[namespaced element]: #namespaced-element 'Definition of Namespaced Element'
+[semantic role]: #semantic-role 'Definition of Semantic Role'
diff --git a/pages/glossary/attribute-value.md b/pages/glossary/attribute-value.md
index 49066d5ac5b..fcee6a9aff3 100755
--- a/pages/glossary/attribute-value.md
+++ b/pages/glossary/attribute-value.md
@@ -17,16 +17,24 @@ Some notable case of attribute value, among others:
 - For attributes that accept [numbers][], the <dfn id="attribute-value:number">attribute value</dfn> 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 <dfn id="attribute-value:tokens-list">attribute value</dfn> 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 <dfn id="attribute-value:aria">attribute value</dfn> is computed as indicated in the [WAI-ARIA specification][] and the [HTML Accessibility API Mappings][html aam].
+- For the `role` attribute, its <dfn id="attribute-value:role">attribute value</dfn> is the first valid token of the value as written in the HTML code.
 
 This list is not exhaustive, and only serves as an illustration for some of the most common cases.
 
 The <dfn id="attribute-value:idl">attribute value</dfn> of an [IDL attribute][] is the value returned on getting it. Note that when an [IDL attribute][] [reflects][reflect] a content attribute, they have the same attribute value.
 
+#### Background
+
+Note that this definition of _attribute value_ differs from the "value of an attribute" as defined in the [DOM][dom attribute value] or [HTML][html attribute value] specifications. The latter is the value as written in the HTML code, while the former is the value after parsing and computing it according to specifications.
+
 [boolean attributes]: https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#boolean-attributes 'HTML Specification of Boolean Attribute'
 [comma separated]: https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#comma-separated-tokens 'HTML Specification of Comma Separated Tokens'
+
+[dom attribute value]][dom-attribute-value]: https://dom.spec.whatwg.org/#concept-attribute-value 'DOM Specification of Attribute Value'
 [enumerated attributes]: https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#enumerated-attribute 'HTML Specification of Enumerated Attribute'
 [idl attribute]: https://heycam.github.io/webidl/#idl-attributes "Definition of Web IDL Attribute (Editor's Draft)"
 [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'
+[html attribute value]: https://html.spec.whatwg.org/multipage/dom.html#attributes 'HTML Specification of Attribute Value'
 [numbers]: https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#numbers 'HTML Specification of Number Parsing'
 [reflect]: https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#reflecting-content-attributes-in-idl-attributes 'HTML specification of Reflecting Content Attributes in IDL Attributes'
 [space separated]: https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#space-separated-tokens 'HTML Specification of Space Separated Tokens'