--- a/ttml1/spec/ttml1-errata.html	Thu Jul 31 19:22:23 2014 -0600
+++ b/ttml1/spec/ttml1-errata.html	Thu Jul 31 21:08:50 2014 -0600
@@ -56,6 +56,8 @@
       marked <span class="diff-del">thus</span>. Changed text marked <span class="diff-chg">thus</span>.</p>
     <h2 id="errors">Known errata as of 31 July 2014</h2>
     <ul>
+      <li><a href="#errata-2.2-1">Correction in TTML1 Section 2.2 Terminology</a>
+          (published 2014-07-31)</li>
       <li><a href="#errata-2.3-1">Correction in TTML1 Section 2.3 Document Conventions</a>
           (published 2014-07-31)</li>
       <li><a href="#errata-5.2-1">Correction in TTML1 Section 5.2 Profiles</a>
@@ -64,6 +66,8 @@
           (published 2014-07-17)</li>
       <li><a href="#errata-8.2.16-1">Correction in TTML1 Section 8.2.16 tts:padding attribute</a>
           (published 2014-07-17)</li>
+      <li><a href="#errata-8.2.17-1">Correction in TTML1 Section 8.2.17 tts:showBackground attribute</a>
+          (published 2014-07-31)</li>
       <li><a href="#errata-10.2.3-1">Correction in TTML1 Section 10.2.3 Duration (dur) attribute</a>
           (published 2014-07-17)</li>
       <li><a href="#errata-C-1">Correction in TTML1 Appendix C - Media Type
@@ -73,6 +77,20 @@
     </ul>
     <h2>Errata</h2>
     <hr />
+    <p id="errata-2.2-1">Correction
+        in <a href="http://www.w3.org/TR/2013/REC-ttml1-20130924/#terms">TTML1 Section 2.2 Terminology</a> (published 2014-07-31) </p>
+    <p class="description"><span class="title-description">Description</span>:</p>
+    Add definitions of <em>Temporally Active</em> and <em>Temporally Active Region</em>.
+    <p class="description"><em><strong><span class="title-correction">Resolution</span></strong></em>:</p>
+    <p>Add following two definitions just prior to the definition of <em>Timed Text</em>:
+    <dl>
+    <dt><span class="diff-add">Temporally Active</span></dt>
+    <dd><p><span class="diff-add">A syntactic or semantic feature, e.g., an element or the presentation of an element,
+    is <em>Temporally Active</em> when the current time of selected time base intersects with the active time interval of the feature.</span></p></dd>
+    <dt><span class="diff-add">Temporally Active Region</span></dt>
+    <dd><p><span class="diff-add">A <em>Region</em> that is <em>Temporally Active</em>.</span></p></dd>
+    </dl>
+    <hr />
     <p id="errata-2.3-1">Correction
         in <a href="http://www.w3.org/TR/2013/REC-ttml1-20130924/#conventions">TTML1 Section 2.3 Document Conventions</a> (published 2014-07-31) </p>
     <p class="description"><span class="title-description">Description</span>:</p>
@@ -114,6 +132,15 @@
     supported padding is minimized<span class="diff-add"> on a per-edge basis</span>. If there are multiple closest supported values equally distant from the computed value<span class="diff-add"> for a given edge</span>, then the value <span class="diff-chg">least</span>
     distant from 0, i.e., the <span class="diff-chg">least</span> padding, is used."</p>
     <hr />
+    <p id="errata-8.2.17-1">Correction
+        in <a href="http://www.w3.org/TR/2013/REC-ttml1-20130924/#style-attribute-showBackground">TTML1 Section 8.2.17 - tts:showBackground attribute</a> (published 2014-07-31) </p>
+    <p class="description"><span class="title-description">Description</span>:</p>
+    Clarify meaning of <code>whenActive</code>.    
+    <p class="description"><em><strong><span class="title-correction">Resolution</span></strong></em>:</p>
+    <p>Add the following paragraph immediately prior to the paragraph starting with "If a computed value of the property ...":</p>
+    <p class="diff-add">A region satisfies the <code>whenActive</code> case if (1) it is a
+    <em>Temporally Active Region</em> and (2) content is selected into the region, where that content is also <em>Temporally Active</em>.</p>
+    <hr />
     <p id="errata-10.2.3-1">Correction
         in <a href="http://www.w3.org/TR/2013/REC-ttml1-20130924/#timing-attribute-dur">TTML1 Section 10.2.3 - dur attribute</a> (published 2014-07-17) </p>
     <p class="description"><span class="title-description">Description</span>:</p>

--- a/ttml2/spec/ttml2.xml	Thu Jul 31 19:22:23 2014 -0600
+++ b/ttml2/spec/ttml2.xml	Thu Jul 31 21:08:50 2014 -0600
@@ -949,6 +949,20 @@
 otherwise determined by the <loc href="#terms-document-processing-context">document processing context</loc>.</p>
 </def>
 </gitem>
+<gitem id="terms-temporally-active">
+<label>[temporally active]</label>
+<def>
+<p>A syntactic or semantic feature, e.g., an element or the presentation of an element, is
+<emph>temporally active</emph> when the current time of selected time base intersects with the
+active time interval of the feature.</p>
+</def>
+</gitem>
+<gitem id="terms-temporally-active-region">
+<label>[temporally active]</label>
+<def>
+<p>A <loc href="#terms-region">region</loc> that is <loc href="#terms-temporally-active">temporally active</loc>.</p>
+</def>
+</gitem>
 <gitem id="terms-timed-text">
 <label>[timed text]</label>
 <def>
@@ -6862,6 +6876,9 @@
 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>A region satisfies the <code>whenActive</code> case if (1) it is a
+<loc href="#terms-temporally-active-region">temporally active region</loc> and (2) content is selected into the region,
+where that content is also <loc href="#terms-temporally-active">temporally active</loc>.</p>
 <p>If a computed value of the property associated with this attribute is not supported,
 then a <loc href="#terms-presentation-processor">presentation processor</loc> must use the value <code>always</code>.</p>
 <p>The <att>tts:showBackground</att> style is illustrated by the following example.</p>