Add background info on extended SC mapping

_rules/descriptive-link-5effbb.md

@@ -50,6 +50,8 @@ The [accessible name][] of each target element together with its [programmatical
 
 ## Background
 
+This rule is designed specifically for [2.4.4 Link Purpose (In Context)][sc244], 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)][sc249] as well. In order to adequately test the [expectation](#expectation), some of the passed examples do not satisfy [2.4.9 Link Purpose (Link only)][sc249].
+
 - [2.4.4 Link Purpose (In Context)](https://www.w3.org/WAI/WCAG21/Understanding/link-purpose-in-context.html)
 - [2.4.9 Link Purpose (Link Only)](https://www.w3.org/WAI/WCAG21/Understanding/link-purpose-link-only.html)
 - [G91: Providing link text that describes the purpose of a link](https://www.w3.org/WAI/WCAG21/Techniques/general/G91)
@@ -329,3 +331,5 @@ An `a` element without the [semantic role][] `link`.
 [presentational roles conflict resolution]: https://www.w3.org/TR/wai-aria-1.1/#conflict_resolution_presentation_none 'Presentational Roles Conflict Resolution'
 [programmatically determined link context]: #programmatically-determined-link-context 'Definition of programmatically determined link context'
 [semantic role]: #semantic-role 'Definition of semantic role'
+[sc244]: https://www.w3.org/TR/WCAG21/#link-purpose-in-context 'Success Criterion 2.4.4: Link Purpose (In Context)'
+[sc249]: https://www.w3.org/TR/WCAG21/#link-purpose-link-only 'Success Criterion 2.4.9: Link Purpose (Link Only)'

_rules/links-with-identical-names-and-context-serve-equivalent-purpose-fd3a94.md

@@ -10,6 +10,11 @@ accessibility_requirements:
     failed: not satisfied
     passed: further testing needed
     inapplicable: further testing needed
+  wcag20:2.4.9: # Link Purpose (Link Only) (AAA)
+    forConformance: true
+    failed: not satisfied
+    passed: further testing needed
+    inapplicable: further testing needed
 input_aspects:
   - DOM Tree
   - CSS Styling
@@ -57,6 +62,8 @@ _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)][sc244], 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)][sc249] as well. In order to adequately test the [expectation](#expectation), some of the passed examples do not satisfy [2.4.9 Link Purpose (Link only)][sc249].
+
 - [Understanding Success Criterion 2.4.4: Link Purpose (In Context)](https://www.w3.org/WAI/WCAG21/Understanding/link-purpose-in-context.html)
 - [HTML Specification - URL parsing](https://html.spec.whatwg.org/#resolving-urls)
 
@@ -370,6 +377,7 @@ These two `span` elements do not have a [semantic role][] of link.
 [programmatically determined link context]: #programmatically-determined-link-context 'Definition of programmatically determined link context'
 [same resource]: #same-resource 'Definition of same resource'
 [sc244]: https://www.w3.org/TR/WCAG21/#link-purpose-in-context 'Success Criterion 2.4.4: Link Purpose (In Context)'
+[sc249]: https://www.w3.org/TR/WCAG21/#link-purpose-link-only 'Success Criterion 2.4.9: Link Purpose (Link Only)'
 [semantic role]: #semantic-role 'Definition of semantic role'
 [shadow tree]: https://dom.spec.whatwg.org/#shadow-tree 'Definition of shadow tree'
 [web page (html)]: #web-page-html 'Definition of web page (HTML)'

_rules/meta-refresh-no-delay-bc659a.md

@@ -58,6 +58,8 @@ Not all major web browsers parse the value of the `content` attribute in the sam
 
 ## Background
 
+This rule is designed specifically for [2.2.1 Timing Adjustable][sc221], which can be satisfied if the time limit is over 20 hours long. All pages that fail this because of a "refresh" `meta` element also do not satisfy [2.2.3 No Timing][sc223] and [3.2.5 Change on Request][sc325]. In order to adequately test the [expectation](#expectation), some of the passed examples do not satisfy [2.2.3 No Timing][sc223] and [3.2.5 Change on Request][sc325].
+
 - [H76: Using meta refresh to create an instant client-side redirect](https://www.w3.org/TR/WCAG-TECHS/H76.html)
 - [F40: Failure of Success Criterion 2.2.1 and 2.2.4 due to using meta redirect with a time limit](https://www.w3.org/TR/WCAG-TECHS/F40.html)
 - [F41: Failure of Success Criterion 2.2.1, 2.2.4, and 3.2.5 due to using meta refresh with a time-out](https://www.w3.org/TR/WCAG-TECHS/F41.html)
@@ -221,3 +223,7 @@ No `http-equiv="refresh"` attribute.
 	<meta http-equiv="refresh" content="foo; URL='https://github.com'" />
 </head>
 ```
+
+[sc221]: https://www.w3.org/TR/WCAG21/#timing-adjustable 'WCAG 2.1 Success Criterion 2.2.1 Timing Adjustable'
+[sc223]: https://www.w3.org/TR/WCAG21/#no-timing 'WCAG 2.1 Success Criterion 2.2.3 No Timing'
+[sc325]: https://www.w3.org/TR/WCAG21/#change-on-request 'WCAG 2.1 Success Criterion 3.2.5 Change on Request'

_rules/meta-viewport-b4f0c3.md

@@ -48,6 +48,8 @@ Desktop browsers ignore the viewport `meta` element, and most modern mobile brow
 
 ## Background
 
+This rule is designed specifically for [1.4.4 Resize text][sc144], which requires that text can be resized up to 200%. Because text that can not be resized up to 200% can not fit in an area of 320 by 256 [CSS pixels][], this rule maps to [1.4.10 Reflow][sc1410] as well. All passed examples in this rule satisfy both success criteria.
+
 - [Understanding Success Criterion 1.4.4: Resize text](https://www.w3.org/WAI/WCAG21/Understanding/resize-text)
 - [HTML Specification - The `meta` element][meta]
 - [The initial-scale, minimum-scale, and maximum-scale properties][maximum-scale]
@@ -267,5 +269,5 @@ This viewport `meta` element does not have a `content` attribute.
 [user-scalable]: https://www.w3.org/TR/css-device-adapt-1/#user-scalable 'The user-scalable property'
 [visible]: #visible 'Definition of visible'
 [css pixels]: https://www.w3.org/TR/css3-values/#reference-pixel 'CSS 3 definition, reference pixel'
-[sc144]: https://www.w3.org/TR/WCAG21/#resize-text 'Success Criterion 1.4.4 Resize text'
-[sc1410]: https://www.w3.org/TR/WCAG21/#reflow 'Success Criterion 1.4.10 Reflow'
+[sc144]: https://www.w3.org/TR/WCAG21/#resize-text 'WCAG 2.1 Success Criterion 1.4.4 Resize text'
+[sc1410]: https://www.w3.org/TR/WCAG21/#reflow 'WCAG 2.1 Success Criterion 1.4.10 Reflow'

_rules/scrollable-element-keyboard-accessible-0ssw9k.md

@@ -10,6 +10,11 @@ accessibility_requirements:
     failed: not satisfied
     passed: further testing needed
     inapplicable: further testing needed
+  wcag20:2.1.3: # Keyboard (No Exceptions) (AAA)
+    forConformance: true
+    failed: not satisfied
+    passed: further testing needed
+    inapplicable: further testing needed
   wcag-technique:G202: # Ensuring keyboard control for all functionality
     forConformance: false
     failed: not satisfied

_rules/text-contrast-afw4f7.md

@@ -55,6 +55,8 @@ For each test target, the [highest possible contrast][] between the [foreground
 
 Passing this rule does not mean that the text has sufficient color contrast. If all background pixels have a low contrast with all foreground pixels, the success criterion is guaranteed to not be satisfied. When some pixels have sufficient contrast, and others do not, legibility should be considered. There is no clear method for determining legibility, which is why this is out of scope for this rule.
 
+This rule is designed specifically for [1.4.3 Contrast (Minimum)][sc143], which has the expected contrast ratio of 4.5:1 (or 3:1 for large text). Because text that fails a contrast ratio of 4.5:1 also fails a contrast ratio of 7:1, this rule maps to [1.4.6 Contrast (Enhanced)][sc146] as well. In order to adequately test the [expectation](#expectation), some of the passed examples do not satisfy [1.4.6 Contrast (Enhanced)][sc146].
+
 When the text color or background color is not specified in the web page, colors from other [origins][] will be used. Testers must ensure colors are not affected by styles from a [user origin][], such as a custom style sheet. Contrast issues cause by specifying the text color but not the background or vise versa, must be tested separately from this rule.
 
 - [Understanding Success Criterion 1.4.3: Contrast (Minimum)](https://www.w3.org/WAI/WCAG21/Understanding/contrast-minimum.html)
@@ -391,6 +393,7 @@ This text is part of a label of a [disabled][] widget, because it is in a `label
 [purely decorative]: https://www.w3.org/TR/WCAG21/#dfn-pure-decoration 'WCAG 2.1, Purely decorative'
 [text node]: https://dom.spec.whatwg.org/#text 'DOM, text node, 2020/07/23'
 [sc143]: https://www.w3.org/TR/WCAG21/#contrast-minimum 'WCAG 2.1, Success criterion 1.4.3 Contrast (Minimum)'
+[sc146]: https://www.w3.org/TR/WCAG21/#contrast-enhanced 'WCAG 2.1, Success criterion 1.4.6 Contrast (Enhanced)'
 [semantic role]: #semantic-role 'Definition of Semantic role'
 [user origin]: https://www.w3.org/TR/css3-cascade/#cascade-origin-user 'CSS 3, user origin'
 [visible]: #visible 'Definition of Visible'

_rules/video-alternative-for-visual-c5a4ea.md

@@ -10,6 +10,11 @@ accessibility_requirements:
     failed: not satisfied
     passed: further testing needed
     inapplicable: further testing needed
+  wcag20:1.2.5: # Audio Description (Prerecorded) (AAA)
+    forConformance: true
+    failed: not satisfied
+    passed: further testing needed
+    inapplicable: further testing needed
   wcag20:1.2.8: # Media Alternative (Prerecorded) (AAA)
     forConformance: true
     failed: not satisfied
@@ -78,6 +83,8 @@ See [Video element description track: accessibility support](https://act-rules.g
 
 ## Background
 
+This rule is designed specifically for [1.2.3 Audio Description or Media Alternative (Prerecorded)][sc123], which expects either audio description or a media alternative. If a video has neither, by definition it also fails for both [1.2.5 Audio Description (Prerecorded)][sc125] and [1.2.8 Media Alternative (Prerecorded)][sc128]. In order to adequately test the [expectation](#expectation) of this rule, some of the passed examples do not satisfy [1.2.5 Audio Description (Prerecorded)][sc125] or [1.2.8 Media Alternative (Prerecorded)][sc128].
+
 - [Understanding Success Criterion 1.2.5: Audio Description (Prerecorded)](https://www.w3.org/WAI/WCAG21/Understanding/audio-description-prerecorded.html)
 - [G78: Providing a second, user-selectable, audio track that includes audio descriptions](https://www.w3.org/WAI/WCAG21/Techniques/general/G78)
 - [H96: Using the track element to provide audio descriptions](https://www.w3.org/WAI/WCAG21/Techniques/html/H96)
@@ -231,3 +238,6 @@ A video element that is not [visible][].
 ```
 
 [visible]: #visible 'Definition of visible'
+[sc123]: https://www.w3.org/TR/WCAG21/#audio-description-or-media-alternative-prerecorded 'WCAG 2.1, Success Criterion 1.2.3 Audio Description or Media Alternative (Prerecorded)'
+[sc125]: https://www.w3.org/TR/WCAG21/#audio-description-prerecorded 'WCAG 2.1, Success Criterion 1.2.5 Audio Description (Prerecorded)'
+[sc128]: https://www.w3.org/TR/WCAG21/#media-alternative-prerecorded 'WCAG 2.1, Success Criterion 1.2.8 Media Alternative (Prerecorded)'