--- a/ttml1/spec/ttml1-changes.html	Wed Aug 28 12:01:51 2013 -0600
+++ b/ttml1/spec/ttml1-changes.html	Wed Aug 28 13:21:15 2013 -0600
@@ -61,6 +61,12 @@
 
 * In 7.1.7, indicate semantic scoping of metadata and animation children of br element.
 
+* In 8, improve language regarding presentation processor behavior when a specified
+  value isn't supported; revise to refer to lack of support for computed value, in
+  which case a specific used value is prescribed.
+
+* In 8, add notes defining meaning of "closest supported value".
+
 * In 8.1.2, remove erroneous sentence stating that style element takes metadata children
   (this support was removed in the sytnax definition and schema before REC was published,
   but this sentence was inadvertently left in the text).
@@ -80,8 +86,6 @@
 * In 8.2.9, elaborate note that explains use of single cell-based length to also include
   case of two cell-based lengths.
 
-* In 8.2.9, add note clarifying the meaning of closest supported value.
-
 * In 8.2.12, correct typo where "initial" value was written, but "computed" value
   intended.
 
@@ -95,10 +99,6 @@
 * In 8.2.13, correct typo where "initial" value was written, but "computed" value
   intended.
 
-* In 8.3.1, add note clarifying the meaning of closest supported value.
-
-* In 8.3.2, add note clarifying the meaning of closest supported value.
-
 * In 8.4.2.1, add note clarifying that the body element, and not the tt element, is the
   outermost element from which content style inheritance occurs.
 

--- a/ttml1/spec/ttml1.xml	Wed Aug 28 12:01:51 2013 -0600
+++ b/ttml1/spec/ttml1.xml	Wed Aug 28 13:21:15 2013 -0600
@@ -3722,8 +3722,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must ignore the attribute.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>ltr</code>.</p>
 <p>The <att>tts:direction</att> style is illustrated by the following example.</p>
 <table id="style-attribute-direction-example-1" role="example">
 <caption>Example Fragment &ndash; Direction</caption>
@@ -3945,9 +3945,8 @@
 </tr>
 </tbody>
 </table>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>before</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>before</code>.</p>
 <p>The <att>tts:displayAlign</att> style is illustrated by the following example.</p>
 <table id="style-attribute-displayAlign-example-1" role="example">
 <caption>Example Fragment &ndash; Display Align</caption>
@@ -4064,9 +4063,12 @@
 If <att>tts:extent</att> is specified on the <el>tt</el> element, then
 the width and height must be expressed in terms of two <loc href="#style-value-length">&lt;length&gt;</loc> specifications,
 and these specifications must be expressed as non-percentage, definite lengths using pixel units.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>auto</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed extent and the supported extent is minimized.</p>
+</note>
 <p>The <att>tts:extent</att> style is illustrated by the following example.</p>
 <table id="style-attribute-extent-example-1" role="example">
 <caption>Example Fragment &ndash; Extent</caption>
@@ -4155,12 +4157,11 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified font family is not available, then a
-presentation processor must attempt to map the specified font family
-to an available font family that has similar typographic
+<p>If a computed value of the property associated with this attribute is not supported, then a
+presentation processor must attempt to map the computed font family
+to a supported font family that has similar typographic
 characteristics, or, in the absence of such a mapping, it must
-interpret the font family as if the value <code>default</code> were
-specified.</p>
+use the value <code>default</code>.</p>
 <p>The <att>tts:fontFamily</att> style is illustrated by the following example.</p>
 <table id="style-attribute-fontFamily-example-1" role="example">
 <caption>Example Fragment &ndash; Font Family</caption>
@@ -4274,9 +4275,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the closest supported value were
-specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
 <note role="elaboration">
 <p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
 the computed font size and the supported font size is minimized.</p>
@@ -4387,12 +4387,8 @@
 <p>Use of the value <code>oblique</code>
 denotes a shear transformation (at an unspecified
 angle) in the inline progression dimension.</p>
-<p>If a specified font style is not available, then a
-presentation processor must attempt to map the specified font style
-to an available font style that has similar typographic
-characteristics, or, in the absence of such a mapping, it must
-interpret the font style as if the value <code>normal</code> were
-specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>normal</code>.</p>
 <p>The <att>tts:fontStyle</att> style is illustrated by the following example.</p>
 <table id="style-attribute-fontStyle-example-1" role="example">
 <caption>Example Fragment &ndash; Font Style</caption>
@@ -4483,12 +4479,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified font weight is not available, then a
-presentation processor must attempt to map the specified font weight
-to an available font weight that has similar typographic
-characteristics, or, in the absence of such a mapping, it must
-interpret the font weight as if the value <code>normal</code> were
-specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>normal</code>.</p>
 <p>The <att>tts:fontWeight</att> style is illustrated by the following example.</p>
 <table id="style-attribute-fontWeight-example-1" role="example">
 <caption>Example Fragment &ndash; Font Weight</caption>
@@ -4582,9 +4574,12 @@
 <p>If specified as a <loc
 href="#style-value-length">&lt;length&gt;</loc>, then the length must
 be non-negative.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>normal</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed line height and the supported line height is minimized.</p>
+</note>
 <p>The <att>tts:lineHeight</att> style is illustrated by the following example.</p>
 <table id="style-attribute-lineHeight-example-1" role="example">
 <caption>Example Fragment &ndash; Line Height</caption>
@@ -4797,9 +4792,12 @@
 is the <emph>x</emph> coordinate, and the second specification is the <emph>y</emph> coordinate.</p>
 <p>If the value of this attribute is <code>auto</code>, then the computed value
 of the style property must be considered to be the same as the origin of the <emph>Root Container Region</emph>.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>auto</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed origin and the supported origin is minimized.</p>
+</note>
 <p>The <att>tts:origin</att> style is illustrated by the following example.</p>
 <table id="style-attribute-origin-example-1" role="example">
 <caption>Example Fragment &ndash; Origin</caption>
@@ -4894,9 +4892,8 @@
 region is <code>visible</code> and if the applicable <att>tts:wrapOption</att>
 style is <code>noWrap</code>.</p>
 </note>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>hidden</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>hidden</code>.</p>
 <p>The <att>tts:overflow</att> style is illustrated by the following example.</p>
 <table id="style-attribute-overflow-example-1" role="example">
 <caption>Example Fragment &ndash; Overflow</caption>
@@ -5018,9 +5015,12 @@
 If four <loc href="#style-value-length">&lt;length&gt;</loc> specifications are provided, then they apply to before, end,
 after, and start edges, respectively.</p>
 <p>The <loc href="#style-value-length">&lt;length&gt;</loc> value(s) used to express padding must be non-negative.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>0px</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed padding and the supported padding is minimized.</p>
+</note>
 <p>The <att>tts:padding</att> style is illustrated by the following example.</p>
 <table id="style-attribute-padding-example-1" role="example">
 <caption>Example Fragment &ndash; Padding</caption>
@@ -5117,9 +5117,8 @@
 processing on a visual medium; if the value is <code>whenActive</code>,
 then the background color of a region is rendered only when some
 content is flowed into the region.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>always</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>always</code>.</p>
 <p>The <att>tts:showBackground</att> style is illustrated by the following example.</p>
 <table id="style-attribute-showBackground-example-1" role="example">
 <caption>Example Fragment &ndash; Show Background</caption>
@@ -5203,9 +5202,8 @@
 </tr>
 </tbody>
 </table>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>start</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>start</code>.</p>
 <p>The <att>tts:textAlign</att> style is illustrated by the following example.</p>
 <table id="style-attribute-textAlign-example-1" role="example">
 <caption>Example Fragment &ndash; Text Align</caption>
@@ -5311,17 +5309,14 @@
 <p>For the purpose of determining applicability of this
 style property, each character child of a <el>p</el> element is
 considered to be enclosed in an anonymous span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>none</code> were specified.</p>
-
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>none</code>.</p>
 <note role="clarification">
 <p>The syntax used above in defining the value of this property is based on the
 value component syntax defined in <bibref ref="css2"/>, &sect; 1.4.2.1. In essence,
 one or more of the values separated by <code>||</code> may appear in the property
 value in any order, such as <code>"noUnderline overline lineThrough"</code>.</p>
 </note>
-
 <p>The <att>tts:textDecoration</att> style is illustrated by the following example.</p>
 <table id="style-attribute-textDecoration-example-1" role="example">
 <caption>Example Fragment &ndash; Text Decoration</caption>
@@ -5434,9 +5429,8 @@
 outline thickness will be a nominal 480 / 10 * 0.1 pixels, i.e., 4.8px,
 without taking into account rasterization effects.</p>
 </note>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>none</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>none</code>.</p>
 <p>The <att>tts:textOutline</att> style is illustrated by the following
 example.</p>
 <table id="style-attribute-textOutline-example-1" role="example">
@@ -5529,9 +5523,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>normal</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>normal</code>.</p>
 <p>The <att>tts:unicodeBidi</att> style is illustrated by the following example.</p>
 <table id="style-attribute-unicodeBidi-example-1" role="example">
 <caption>Example Fragment &ndash; Unicode Bidirectionality</caption>
@@ -5630,9 +5623,8 @@
 span.</p>
 <p>The <att>tts:visibility</att> style has no affect on content layout or
 composition, but merely determines whether composed content is visible or not.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>visible</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>visible</code>.</p>
 <p>The <att>tts:visibility</att> style is illustrated by the following example.</p>
 <table id="style-attribute-visibility-example-1" role="example">
 <caption>Example Fragment &ndash; Visibility</caption>
@@ -5745,9 +5737,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>wrap</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>wrap</code>.</p>
 <p>The <att>tts:wrapOption</att> style is illustrated by the following example.</p>
 <table id="style-attribute-wrapOption-example-1" role="example">
 <caption>Example Fragment &ndash; Wrap Option</caption>
@@ -5839,9 +5830,8 @@
 </tr>
 </tbody>
 </table>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>lrtb</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>lrtb</code>.</p>
 <p>The <att>tts:writingMode</att> style is illustrated by the following example.</p>
 <table id="style-attribute-writingMode-example-1" role="example">
 <caption>Example Fragment &ndash; Writing Mode</caption>
@@ -5951,9 +5941,12 @@
 <p>The semantics of the value <code>auto</code> are those defined by
 <bibref ref="xsl11"/>, &sect; 7.30.18, where the <el>tt</el> element
 is considered to establish the root stacking context.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>auto</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed z-index and the supported z-index is minimized.</p>
+</note>
 <p>The <att>tts:zIndex</att> style is illustrated by the following example.</p>
 <table id="style-attribute-zIndex-example-1" role="example">
 <caption>Example Fragment &ndash; Z Index</caption>

--- a/ttml2/spec/ttml2.xml	Wed Aug 28 12:01:51 2013 -0600
+++ b/ttml2/spec/ttml2.xml	Wed Aug 28 13:21:15 2013 -0600
@@ -3799,9 +3799,17 @@
 <p>If no border width is specified in the value of the <att>tts:border</att> property,
 then the border width must be interpreted as if a width of
 <code>medium</code> were specified.</p>
+<p>If a computed value of the border width associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed border width and the supported border width is minimized.</p>
+</note>
 <p>If no border style is specified in the value of the <att>tts:border</att> property,
 then the border style must be interpreted as if a style of
 <code>none</code> were specified.</p>
+<p>If a computed value of the border style associated with this attribute is not supported,
+then a presentation processor must use the value <code>solid</code>.</p>
 <p>If no border color is specified in the value of the <att>tts:border</att> property,
 then the border color must be interpreted as if a color equal
 to the computed value of the element's <code>tts:color</code> property were specified.</p>
@@ -3991,8 +3999,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must ignore the attribute.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>ltr</code>.</p>
 <p>The <att>tts:direction</att> style is illustrated by the following example.</p>
 <table id="style-attribute-direction-example-1" role="example">
 <caption>Example Fragment &ndash; Direction</caption>
@@ -4214,9 +4222,8 @@
 </tr>
 </tbody>
 </table>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>before</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>before</code>.</p>
 <p>The <att>tts:displayAlign</att> style is illustrated by the following example.</p>
 <table id="style-attribute-displayAlign-example-1" role="example">
 <caption>Example Fragment &ndash; Display Align</caption>
@@ -4333,9 +4340,12 @@
 If <att>tts:extent</att> is specified on the <el>tt</el> element, then
 the width and height must be expressed in terms of two <loc href="#style-value-length">&lt;length&gt;</loc> specifications,
 and these specifications must be expressed as non-percentage, definite lengths using pixel units.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>auto</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed extent and the supported extent is minimized.</p>
+</note>
 <p>The <att>tts:extent</att> style is illustrated by the following example.</p>
 <table id="style-attribute-extent-example-1" role="example">
 <caption>Example Fragment &ndash; Extent</caption>
@@ -4424,12 +4434,11 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified font family is not available, then a
-presentation processor must attempt to map the specified font family
-to an available font family that has similar typographic
+<p>If a computed value of the property associated with this attribute is not supported, then a
+presentation processor must attempt to map the computed font family
+to a supported font family that has similar typographic
 characteristics, or, in the absence of such a mapping, it must
-interpret the font family as if the value <code>default</code> were
-specified.</p>
+use the value <code>default</code>.</p>
 <p>The <att>tts:fontFamily</att> style is illustrated by the following example.</p>
 <table id="style-attribute-fontFamily-example-1" role="example">
 <caption>Example Fragment &ndash; Font Family</caption>
@@ -4543,9 +4552,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the closest supported value were
-specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
 <note role="elaboration">
 <p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
 the computed font size and the supported font size is minimized.</p>
@@ -4656,12 +4664,8 @@
 <p>Use of the value <code>oblique</code>
 denotes a shear transformation (at an unspecified
 angle) in the inline progression dimension.</p>
-<p>If a specified font style is not available, then a
-presentation processor must attempt to map the specified font style
-to an available font style that has similar typographic
-characteristics, or, in the absence of such a mapping, it must
-interpret the font style as if the value <code>normal</code> were
-specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>normal</code>.</p>
 <p>The <att>tts:fontStyle</att> style is illustrated by the following example.</p>
 <table id="style-attribute-fontStyle-example-1" role="example">
 <caption>Example Fragment &ndash; Font Style</caption>
@@ -4752,12 +4756,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified font weight is not available, then a
-presentation processor must attempt to map the specified font weight
-to an available font weight that has similar typographic
-characteristics, or, in the absence of such a mapping, it must
-interpret the font weight as if the value <code>normal</code> were
-specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>normal</code>.</p>
 <p>The <att>tts:fontWeight</att> style is illustrated by the following example.</p>
 <table id="style-attribute-fontWeight-example-1" role="example">
 <caption>Example Fragment &ndash; Font Weight</caption>
@@ -4851,9 +4851,12 @@
 <p>If specified as a <loc
 href="#style-value-length">&lt;length&gt;</loc>, then the length must
 be non-negative.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>normal</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed line height and the supported line height is minimized.</p>
+</note>
 <p>The <att>tts:lineHeight</att> style is illustrated by the following example.</p>
 <table id="style-attribute-lineHeight-example-1" role="example">
 <caption>Example Fragment &ndash; Line Height</caption>
@@ -5076,9 +5079,12 @@
 is the <emph>x</emph> coordinate, and the second specification is the <emph>y</emph> coordinate.</p>
 <p>If the value of this attribute is <code>auto</code>, then the computed value
 of the style property must be considered to be the same as the origin of the <emph>Root Container Region</emph>.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>auto</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed origin and the supported origin is minimized.</p>
+</note>
 <p>The <att>tts:origin</att> style is illustrated by the following example.</p>
 <table id="style-attribute-origin-example-1" role="example">
 <caption>Example Fragment &ndash; Origin</caption>
@@ -5173,9 +5179,8 @@
 region is <code>visible</code> and if the applicable <att>tts:wrapOption</att>
 style is <code>noWrap</code>.</p>
 </note>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>hidden</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>hidden</code>.</p>
 <p>The <att>tts:overflow</att> style is illustrated by the following example.</p>
 <table id="style-attribute-overflow-example-1" role="example">
 <caption>Example Fragment &ndash; Overflow</caption>
@@ -5301,9 +5306,12 @@
 If four <loc href="#style-value-length">&lt;length&gt;</loc> specifications are provided, then they apply to before, end,
 after, and start edges, respectively.</p>
 <p>The <loc href="#style-value-length">&lt;length&gt;</loc> value(s) used to express padding must be non-negative.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>0px</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed padding and the supported padding is minimized.</p>
+</note>
 <p>The <att>tts:padding</att> style is illustrated by the following example.</p>
 <ednote>
 <name>Enhance Padding Example</name>
@@ -5406,9 +5414,8 @@
 processing on a visual medium; if the value is <code>whenActive</code>,
 then the background color of a region is rendered only when some
 content is flowed into the region.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>always</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>always</code>.</p>
 <p>The <att>tts:showBackground</att> style is illustrated by the following example.</p>
 <table id="style-attribute-showBackground-example-1" role="example">
 <caption>Example Fragment &ndash; Show Background</caption>
@@ -5492,9 +5499,8 @@
 </tr>
 </tbody>
 </table>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>start</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>start</code>.</p>
 <p>The <att>tts:textAlign</att> style is illustrated by the following example.</p>
 <table id="style-attribute-textAlign-example-1" role="example">
 <caption>Example Fragment &ndash; Text Align</caption>
@@ -5600,17 +5606,14 @@
 <p>For the purpose of determining applicability of this
 style property, each character child of a <el>p</el> element is
 considered to be enclosed in an anonymous span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>none</code> were specified.</p>
-
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>none</code>.</p>
 <note role="clarification">
 <p>The syntax used above in defining the value of this property is based on the
 value component syntax defined in <bibref ref="css2"/>, &sect; 1.4.2.1. In essence,
 one or more of the values separated by <code>||</code> may appear in the property
 value in any order, such as <code>"noUnderline overline lineThrough"</code>.</p>
 </note>
-
 <p>The <att>tts:textDecoration</att> style is illustrated by the following example.</p>
 <table id="style-attribute-textDecoration-example-1" role="example">
 <caption>Example Fragment &ndash; Text Decoration</caption>
@@ -5723,9 +5726,8 @@
 <code>tbrl</code> or <code>tblr</code>, respectively. Glyphs from vertical scripts are not
 affected.</p>
 <p>If a vertical writing mode does not apply, then this style property has no effect.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>mixed</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>mixed</code>.</p>
 <p>The <att>tts:textOrientation</att> style is illustrated by the following
 example.</p>
 <ednote>
@@ -5804,9 +5806,8 @@
 outline thickness will be a nominal 480 / 10 * 0.1 pixels, i.e., 4.8px,
 without taking into account rasterization effects.</p>
 </note>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>none</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>none</code>.</p>
 <p>The <att>tts:textOutline</att> style is illustrated by the following
 example.</p>
 <table id="style-attribute-textOutline-example-1" role="example">
@@ -5899,9 +5900,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>normal</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>normal</code>.</p>
 <p>The <att>tts:unicodeBidi</att> style is illustrated by the following example.</p>
 <table id="style-attribute-unicodeBidi-example-1" role="example">
 <caption>Example Fragment &ndash; Unicode Bidirectionality</caption>
@@ -6000,9 +6000,8 @@
 span.</p>
 <p>The <att>tts:visibility</att> style has no affect on content layout or
 composition, but merely determines whether composed content is visible or not.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>visible</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>visible</code>.</p>
 <p>The <att>tts:visibility</att> style is illustrated by the following example.</p>
 <table id="style-attribute-visibility-example-1" role="example">
 <caption>Example Fragment &ndash; Visibility</caption>
@@ -6115,9 +6114,8 @@
 <p>For the purpose of determining applicability of this style property,
 each character child of a <el>p</el> element is considered to be enclosed in an anonymous
 span.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>wrap</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>wrap</code>.</p>
 <p>The <att>tts:wrapOption</att> style is illustrated by the following example.</p>
 <table id="style-attribute-wrapOption-example-1" role="example">
 <caption>Example Fragment &ndash; Wrap Option</caption>
@@ -6209,9 +6207,8 @@
 </tr>
 </tbody>
 </table>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>lrtb</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the value <code>lrtb</code>.</p>
 <p>The <att>tts:writingMode</att> style is illustrated by the following example.</p>
 <table id="style-attribute-writingMode-example-1" role="example">
 <caption>Example Fragment &ndash; Writing Mode</caption>
@@ -6321,9 +6318,12 @@
 <p>The semantics of the value <code>auto</code> are those defined by
 <bibref ref="xsl11"/>, &sect; 7.30.18, where the <el>tt</el> element
 is considered to establish the root stacking context.</p>
-<p>If a specified value of this attribute is not supported,
-then a presentation processor must interpret the attribute as if the
-value <code>auto</code> were specified.</p>
+<p>If a computed value of the property associated with this attribute is not supported,
+then a presentation processor must use the closest supported value.</p>
+<note role="elaboration">
+<p>In this context, the phrase <emph>closest supported value</emph> means the value for which the Euclidean distance between
+the computed z-index and the supported z-index is minimized.</p>
+</note>
 <p>The <att>tts:zIndex</att> style is illustrated by the following example.</p>
 <table id="style-attribute-zIndex-example-1" role="example">
 <caption>Example Fragment &ndash; Z Index</caption>