- [imsc] second pass at addressing ISSUE-309
authorpal@sandflow.org
Fri, 11 Jul 2014 18:43:33 -0700
changeset 651 c6af2ff635f9
parent 637 e78629db1b60
child 652 05fcca85e051
- [imsc] second pass at addressing ISSUE-309
ttml-ww-profiles/ttml-ww-profiles.html
ttml-ww-profiles/ttml-ww-profiles.source.html
--- a/ttml-ww-profiles/ttml-ww-profiles.html	Mon Jun 16 20:33:15 2014 -0700
+++ b/ttml-ww-profiles/ttml-ww-profiles.html	Fri Jul 11 18:43:33 2014 -0700
@@ -64,7 +64,7 @@
 }
 
 code {
-    color:  #ff4500;
+    color:  #C83500;
 }
 
 /* --- TOC --- */
@@ -217,11 +217,11 @@
   </p>
   <h1 class="title p-name" id="title" property="dcterms:title">TTML Text and Image Profiles for Internet Media Subtitles and Captions 1.0</h1>
   
-  <h2 property="dcterms:issued" datatype="xsd:dateTime" content="2014-06-17T10:28:18.000Z" id="w3c-first-public-working-draft-17-june-2014"><abbr title="World Wide Web Consortium">W3C</abbr> First Public Working Draft <time class="dt-published" datetime="2014-06-17">17 June 2014</time></h2>
+  <h2 property="dcterms:issued" datatype="xsd:dateTime" content="2014-07-12T08:41:32.000Z" id="w3c-first-public-working-draft-12-july-2014"><abbr title="World Wide Web Consortium">W3C</abbr> First Public Working Draft <time class="dt-published" datetime="2014-07-12">12 July 2014</time></h2>
   <dl>
     
       <dt>This version:</dt>
-      <dd><a class="u-url" href="http://www.w3.org/TR/2014/WD-ttml-imsc1-20140617/">http://www.w3.org/TR/2014/WD-ttml-imsc1-20140617/</a></dd>
+      <dd><a class="u-url" href="http://www.w3.org/TR/2014/WD-ttml-imsc1-20140712/">http://www.w3.org/TR/2014/WD-ttml-imsc1-20140712/</a></dd>
       <dt>Latest published version:</dt>
       <dd><a href="http://www.w3.org/TR/ttml-imsc1/">http://www.w3.org/TR/ttml-imsc1/</a></dd>
     
@@ -342,7 +342,7 @@
       
     
   
-</section><section id="toc"><h2 class="introductory" aria-level="1" role="heading" id="h2_toc">Table of Contents</h2><ul class="toc" role="directory" id="respecContents"><li class="tocline"><a href="#scope" class="tocxref"><span class="secno">1. </span>Scope</a></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">2. </span>Conformance</a></li><li class="tocline"><a href="#profiles" class="tocxref"><span class="secno">3. </span>Profiles</a><ul class="toc"><li class="tocline"><a href="#general" class="tocxref"><span class="secno">3.1 </span>General</a></li><li class="tocline"><a href="#text-profile" class="tocxref"><span class="secno">3.2 </span>Text Profile</a></li><li class="tocline"><a href="#image-profile" class="tocxref"><span class="secno">3.3 </span>Image Profile</a></li></ul></li><li class="tocline"><a href="#common-constraints" class="tocxref"><span class="secno">4. </span>Common Constraints</a><ul class="toc"><li class="tocline"><a href="#document-encoding" class="tocxref"><span class="secno">4.1 </span>Document Encoding</a></li><li class="tocline"><a href="#namespaces" class="tocxref"><span class="secno">4.2 </span>Namespaces</a></li><li class="tocline"><a href="#related-video-object" class="tocxref"><span class="secno">4.3 </span>Related Video Object</a></li><li class="tocline"><a href="#synchronization" class="tocxref"><span class="secno">4.4 </span>Synchronization</a></li><li class="tocline"><a href="#extensions" class="tocxref"><span class="secno">4.5 </span>Extensions</a><ul class="toc"><li class="tocline"><a href="#ttp-aspectRatio" class="tocxref"><span class="secno">4.5.1 </span>ittp:aspectRatio</a></li><li class="tocline"><a href="#ttp-progressivelyDecodable" class="tocxref"><span class="secno">4.5.2 </span>ittp:progressivelyDecodable</a></li><li class="tocline"><a href="#tts-forcedDisplay" class="tocxref"><span class="secno">4.5.3 </span>itts:forcedDisplay</a></li></ul></li><li class="tocline"><a href="#region" class="tocxref"><span class="secno">4.6 </span>Region</a><ul class="toc"><li class="tocline"><a href="#presented-region" class="tocxref"><span class="secno">4.6.1 </span>Presented Region</a></li><li class="tocline"><a href="#dimensions-and-position" class="tocxref"><span class="secno">4.6.2 </span>Dimensions and Position</a></li><li class="tocline"><a href="#maximum-number" class="tocxref"><span class="secno">4.6.3 </span>Maximum number</a></li></ul></li><li class="tocline"><a href="#hypothetical-render-model-1" class="tocxref"><span class="secno">4.7 </span>Hypothetical Render Model</a></li><li class="tocline"><a href="#common-features" class="tocxref"><span class="secno">4.8 </span>Features</a></li></ul></li><li class="tocline"><a href="#text-profile-constraints" class="tocxref"><span class="secno">5. </span>Text Profile Constraints</a><ul class="toc"><li class="tocline"><a href="#text-profile-designator" class="tocxref"><span class="secno">5.1 </span>Profile Designator</a></li><li class="tocline"><a href="#recommended-character-sets" class="tocxref"><span class="secno">5.2 </span>Recommended Character Sets</a></li><li class="tocline"><a href="#features" class="tocxref"><span class="secno">5.3 </span>Features</a></li></ul></li><li class="tocline"><a href="#image-profile-constraints" class="tocxref"><span class="secno">6. </span>Image Profile Constraints</a><ul class="toc"><li class="tocline"><a href="#image-profile-designator" class="tocxref"><span class="secno">6.1 </span>Profile Designator</a></li><li class="tocline"><a href="#presented-image" class="tocxref"><span class="secno">6.2 </span>Presented Image</a><ul class="toc"><li class="tocline"><a href="#definition" class="tocxref"><span class="secno">6.2.1 </span>Definition</a></li><li class="tocline"><a href="#number-per-region" class="tocxref"><span class="secno">6.2.2 </span>Number per Region</a></li></ul></li><li class="tocline"><a href="#div-element" class="tocxref"><span class="secno">6.3 </span><code>div</code> element</a></li><li class="tocline"><a href="#features-1" class="tocxref"><span class="secno">6.4 </span>Features</a></li></ul></li><li class="tocline"><a href="#hypothetical-render-model" class="tocxref"><span class="secno">7. </span>Hypothetical Render Model</a><ul class="toc"><li class="tocline"><a href="#performance-model" class="tocxref"><span class="secno">7.1 </span>Performance Model</a><ul class="toc"><li class="tocline"><a href="#overview" class="tocxref"><span class="secno">7.1.1 </span>Overview</a></li><li class="tocline"><a href="#general-1" class="tocxref"><span class="secno">7.1.2 </span>General</a></li><li class="tocline"><a href="#paint-regions" class="tocxref"><span class="secno">7.1.3 </span>Paint Regions</a></li><li class="tocline"><a href="#paint-images" class="tocxref"><span class="secno">7.1.4 </span>Paint Images</a></li><li class="tocline"><a href="#paint-text" class="tocxref"><span class="secno">7.1.5 </span>Paint Text</a></li></ul></li><li class="tocline"><a href="#reference-fonts" class="tocxref"><span class="secno">7.2 </span>Reference Fonts</a></li></ul></li><li class="tocline"><a href="#recommended-unicode-code-points-per-language" class="tocxref"><span class="secno">A. </span>Recommended Character Sets</a></li><li class="tocline"><a href="#features-and-extensions" class="tocxref"><span class="secno">B. </span>Extensions</a><ul class="toc"><li class="tocline"><a href="#general-2" class="tocxref"><span class="secno">B.1 </span>General</a></li><li class="tocline"><a href="#progressivelydecodable" class="tocxref"><span class="secno">B.2 </span>#progressivelyDecodable</a></li><li class="tocline"><a href="#aspectratio" class="tocxref"><span class="secno">B.3 </span>#aspectRatio</a></li><li class="tocline"><a href="#forceddisplay" class="tocxref"><span class="secno">B.4 </span>#forcedDisplay</a></li></ul></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">C. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">C.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">C.2 </span>Informative references</a></li></ul></li></ul></section>
+</section><section id="toc"><h2 class="introductory" aria-level="1" role="heading" id="h2_toc">Table of Contents</h2><ul class="toc" role="directory" id="respecContents"><li class="tocline"><a href="#scope" class="tocxref"><span class="secno">1. </span>Scope</a></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">2. </span>Conformance</a></li><li class="tocline"><a href="#profiles" class="tocxref"><span class="secno">3. </span>Profiles</a><ul class="toc"><li class="tocline"><a href="#general" class="tocxref"><span class="secno">3.1 </span>General</a></li><li class="tocline"><a href="#text-profile" class="tocxref"><span class="secno">3.2 </span>Text Profile</a></li><li class="tocline"><a href="#image-profile" class="tocxref"><span class="secno">3.3 </span>Image Profile</a></li></ul></li><li class="tocline"><a href="#common-constraints" class="tocxref"><span class="secno">4. </span>Common Constraints</a><ul class="toc"><li class="tocline"><a href="#document-encoding" class="tocxref"><span class="secno">4.1 </span>Document Encoding</a></li><li class="tocline"><a href="#namespaces" class="tocxref"><span class="secno">4.2 </span>Namespaces</a></li><li class="tocline"><a href="#related-video-object" class="tocxref"><span class="secno">4.3 </span>Related Video Object</a></li><li class="tocline"><a href="#synchronization" class="tocxref"><span class="secno">4.4 </span>Synchronization</a></li><li class="tocline"><a href="#extensions" class="tocxref"><span class="secno">4.5 </span>Extensions</a><ul class="toc"><li class="tocline"><a href="#ttp-aspectRatio" class="tocxref"><span class="secno">4.5.1 </span>ittp:aspectRatio</a></li><li class="tocline"><a href="#ttp-progressivelyDecodable" class="tocxref"><span class="secno">4.5.2 </span>ittp:progressivelyDecodable</a></li><li class="tocline"><a href="#tts-forcedDisplay" class="tocxref"><span class="secno">4.5.3 </span>itts:forcedDisplay</a></li><li class="tocline"><a href="#ttm-altText" class="tocxref"><span class="secno">4.5.4 </span>ittm:altText</a></li></ul></li><li class="tocline"><a href="#region" class="tocxref"><span class="secno">4.6 </span>Region</a><ul class="toc"><li class="tocline"><a href="#presented-region" class="tocxref"><span class="secno">4.6.1 </span>Presented Region</a></li><li class="tocline"><a href="#dimensions-and-position" class="tocxref"><span class="secno">4.6.2 </span>Dimensions and Position</a></li><li class="tocline"><a href="#maximum-number" class="tocxref"><span class="secno">4.6.3 </span>Maximum number</a></li></ul></li><li class="tocline"><a href="#hypothetical-render-model-1" class="tocxref"><span class="secno">4.7 </span>Hypothetical Render Model</a></li><li class="tocline"><a href="#common-features" class="tocxref"><span class="secno">4.8 </span>Features</a></li></ul></li><li class="tocline"><a href="#text-profile-constraints" class="tocxref"><span class="secno">5. </span>Text Profile Constraints</a><ul class="toc"><li class="tocline"><a href="#text-profile-designator" class="tocxref"><span class="secno">5.1 </span>Profile Designator</a></li><li class="tocline"><a href="#recommended-character-sets" class="tocxref"><span class="secno">5.2 </span>Recommended Character Sets</a></li><li class="tocline"><a href="#features" class="tocxref"><span class="secno">5.3 </span>Features</a></li></ul></li><li class="tocline"><a href="#image-profile-constraints" class="tocxref"><span class="secno">6. </span>Image Profile Constraints</a><ul class="toc"><li class="tocline"><a href="#image-profile-designator" class="tocxref"><span class="secno">6.1 </span>Profile Designator</a></li><li class="tocline"><a href="#presented-image" class="tocxref"><span class="secno">6.2 </span>Presented Image</a><ul class="toc"><li class="tocline"><a href="#definition" class="tocxref"><span class="secno">6.2.1 </span>Definition</a></li><li class="tocline"><a href="#number-per-region" class="tocxref"><span class="secno">6.2.2 </span>Number per Region</a></li></ul></li><li class="tocline"><a href="#div-element" class="tocxref"><span class="secno">6.3 </span><code>div</code> element</a></li><li class="tocline"><a href="#features-1" class="tocxref"><span class="secno">6.4 </span>Features</a></li></ul></li><li class="tocline"><a href="#hypothetical-render-model" class="tocxref"><span class="secno">7. </span>Hypothetical Render Model</a><ul class="toc"><li class="tocline"><a href="#performance-model" class="tocxref"><span class="secno">7.1 </span>Performance Model</a><ul class="toc"><li class="tocline"><a href="#overview" class="tocxref"><span class="secno">7.1.1 </span>Overview</a></li><li class="tocline"><a href="#general-1" class="tocxref"><span class="secno">7.1.2 </span>General</a></li><li class="tocline"><a href="#paint-regions" class="tocxref"><span class="secno">7.1.3 </span>Paint Regions</a></li><li class="tocline"><a href="#paint-images" class="tocxref"><span class="secno">7.1.4 </span>Paint Images</a></li><li class="tocline"><a href="#paint-text" class="tocxref"><span class="secno">7.1.5 </span>Paint Text</a></li></ul></li><li class="tocline"><a href="#reference-fonts" class="tocxref"><span class="secno">7.2 </span>Reference Fonts</a></li></ul></li><li class="tocline"><a href="#recommended-unicode-code-points-per-language" class="tocxref"><span class="secno">A. </span>Recommended Character Sets</a></li><li class="tocline"><a href="#wcag-applications" class="tocxref"><span class="secno">B. </span>WCAG Considerations</a></li><li class="tocline"><a href="#features-and-extensions" class="tocxref"><span class="secno">C. </span>Extensions</a><ul class="toc"><li class="tocline"><a href="#general-2" class="tocxref"><span class="secno">C.1 </span>General</a></li><li class="tocline"><a href="#progressivelydecodable" class="tocxref"><span class="secno">C.2 </span>#progressivelyDecodable</a></li><li class="tocline"><a href="#aspectratio" class="tocxref"><span class="secno">C.3 </span>#aspectRatio</a></li><li class="tocline"><a href="#forceddisplay" class="tocxref"><span class="secno">C.4 </span>#forcedDisplay</a></li></ul></li><li class="tocline"><a href="#alttext" class="tocxref"><span class="secno">D. </span>#altText</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">E. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">E.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">E.2 </span>Informative references</a></li></ul></li></ul></section>
 
   
 
@@ -382,11 +382,16 @@
       <h3 aria-level="2" role="heading" id="h3_general"><span class="secno">3.1 </span>General</h3>
 
       <p>A subtitle document <em class="rfc2119" title="SHALL NOT">SHALL NOT</em> conform to the Text and Image Profiles simultaneously.</p>
-
-      <p class="NOTE">Some applications require the same subtitle/caption content to be available in both text and image form
-      simultaneously (see [<cite><a class="bibref" href="#bib-WCAG20">WCAG20</a></cite>] for instance). For these applications, two distinct subtitle documents, one conforming to the
-      Text Profile and the other conforming to the Image Profile, can be offered.</p>
-    </section>
+			
+			<p>In applications that require subtitle/caption content in image form to be simultaneously available in text form, two distinct subtitle documents, one conforming to the Text Profile and the other conforming to the Image Profile, <em class="rfc2119" title="SHOULD">SHOULD</em> be offered. In addition, the Text Profile subtitle document <em class="rfc2119" title="SHOULD">SHOULD</em> be associated with the Image Profile subtitle document such that, when image content is encountered, assistive technologies have access to its corresponding text form.</p>
+			
+						
+			<div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_1"><span>Note</span></div><p class="">The <code>ittm:altText</code> element specified <a href="#ttm-altText" class="sec-ref"><span class="secno">4.5.4</span> <span class="sec-title">ittm:altText</span></a> also allows text equivalent string to be associated with an image, e.g. to support indexation of the content and also facilitate quality checking of the document during authoring.</p></div>
+			
+			
+			<p>Annex <a href="#wcag-applications" class="sec-ref"><span class="secno">B.</span> <span class="sec-title">WCAG Considerations</span></a> specifically discusses this specification in the context of the [<cite><a class="bibref" href="#bib-WCAG20">WCAG20</a></cite>] guidelines.
+
+    </p></section>
 
     <section id="text-profile">
       <h3 aria-level="2" role="heading" id="h3_text-profile"><span class="secno">3.2 </span>Text Profile</h3>
@@ -432,6 +437,16 @@
 
         <tbody>
           <tr>
+            <td>XML</td>
+
+            <td>xml</td>
+
+            <td>http://www.w3.org/XML/1998/namespace</td>
+
+            <td>[<cite><a class="bibref" href="#bib-xml-names">xml-names</a></cite>]</td>
+          </tr>
+
+          <tr>
             <td>TT Parameter</td>
 
             <td>ttp</td>
@@ -490,6 +505,16 @@
 
             <td><em>This specification</em></td>
           </tr>
+					
+					<tr>
+            <td>IMSC 1.0 Metadata</td>
+
+            <td>ittm</td>
+
+            <td>http://www.w3.org/ns/ttml/profile/imsc1#metadata</td>
+
+            <td><em>This specification</em></td>
+          </tr>
 
           <tr>
             <td>IMSC 1.0 Extension</td>
@@ -551,7 +576,7 @@
       <p>If <code>ttp:frameRate</code> is specified, then the product of <code>ttp:frameRate</code> and
       <code>ttp:frameRateMultiplier</code> <em class="rfc2119" title="SHALL">SHALL</em> be the frame rate of the related video object.</p>
 
-      <div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_1"><span>Note</span></div><p class="">A document can be made independent of the frame rate of the related video object by never using the
+      <div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_2"><span>Note</span></div><p class="">A document can be made independent of the frame rate of the related video object by never using the
       <em>frames</em> term in a time expression: as specified in <a href="#common-features" class="sec-ref"><span class="secno">4.8</span> <span class="sec-title">Features</span></a>, <code>ttp:frameRate</code> is
       required only if the document includes one or more time expressions that uses the <em>frames</em> term.</p></div>
     </section>
@@ -594,7 +619,7 @@
 
         <p><code>ittp:aspectRatio</code> <em class="rfc2119" title="SHALL NOT">SHALL NOT</em> be present if <code>tts:extent</code> is present.<br></p>
 
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_2"><span>Note</span></div><p class="">As specified in Section <a href="#common-features" class="sec-ref"><span class="secno">4.8</span> <span class="sec-title">Features</span></a>, <code>tts:extent</code> is present if the
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_3"><span>Note</span></div><p class="">As specified in Section <a href="#common-features" class="sec-ref"><span class="secno">4.8</span> <span class="sec-title">Features</span></a>, <code>tts:extent</code> is present if the
         <code>px</code> length measure is used anywhere within the document.</p></div>
 
         <p>Integer pixel positions on the related video object frame computed from real percentage length values <em class="rfc2119" title="SHALL">SHALL</em> use half-up
@@ -643,7 +668,7 @@
         <p>A <code>ittp:progressivelyDecodable</code> attribute is considered to be significant only when specified on the
         <code>tt</code> element.</p>
 
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_3"><span>Note</span></div><p class="">The placement and use of <code>div</code>, <code>region</code> and <code>span</code> that contain time
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_4"><span>Note</span></div><p class="">The placement and use of <code>div</code>, <code>region</code> and <code>span</code> that contain time
         attributes, and the use of <code>set</code> are constrained when <code>ittp:progressivelyDecodable="true"</code>
         .</p></div>
       </section>
@@ -705,17 +730,50 @@
           </tbody>
         </table>
 				
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_4"><span>Note</span></div><p class="">Although <code>itts:forcedDisplay</code>, like all the TTML style attributes, has no defined semantics on a
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_5"><span>Note</span></div><p class="">Although <code>itts:forcedDisplay</code>, like all the TTML style attributes, has no defined semantics on a
         <code>br</code> content element, <code>itts:forcedDisplay</code> will apply to a <code>br</code> content element if it is
         either defined on an ancestor content element of the <code>br</code> content element or it is applied to a region element
         corresponding to a region that the <code>br</code> content element is being flowed into.</p></div>
 				
-				<div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_5"><span>Note</span></div><p class="">The algorithm for selecting subtitle and caption tracks based on user preference and content metadata is
+				<div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_6"><span>Note</span></div><p class="">The algorithm for selecting subtitle and caption tracks based on user preference and content metadata is
         not specified here.</p></div>
 				
-				<div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_6"><span>Note</span></div><p class="">Future versions of [<cite><a class="bibref" href="#bib-TTML1">TTML1</a></cite>] might introduce more generic mechanisms for conditional display of content elements.</p></div>
+				<div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_7"><span>Note</span></div><p class="">Future versions of [<cite><a class="bibref" href="#bib-TTML1">TTML1</a></cite>] might introduce more generic mechanisms for conditional display of content elements.</p></div>
       </section>
-    </section>
+    
+		  <section id="ttm-altText" typeof="bibo:Chapter" resource="#ttm-altText" rel="bibo:Chapter">
+        <h4 aria-level="3" role="heading" id="h4_ttm-altText"><span class="secno">4.5.4 </span>ittm:altText</h4>
+
+        <p><code>ittm:altText</code> allows an author to provide a text string equivalent for an element, typically an image. This text equivalent <em class="rfc2119" title="MAY">MAY</em> be used to support indexation of the content and also facilitate quality checking of the document during authoring.</p>
+				
+			  <p>The <code>ittm:altText</code> element <em class="rfc2119" title="SHALL">SHALL</em> conform to the following syntax:</p>
+
+        <table class="syntax">
+          <tbody>
+            <tr>
+              <td>
+                <div class="exampleInner">
+                  <pre>&lt;ittm:altText
+  xml:id = ID
+  xml:lang = string
+  xml:space = (default|preserve)
+  {any attribute not in the IMSC 1.0 Metadata namespace}&gt;
+  Content: #PCDATA
+&lt;/ittm:altText&gt;
+</pre>
+                </div>
+              </td>
+            </tr>
+          </tbody>
+        </table>
+				
+				<p><a href="#image-profile-constraints" class="sec-ref"><span class="secno">6.</span> <span class="sec-title">Image Profile Constraints</span></a> specifies the use of the <code>ittm:altText</code> element with images.</p>
+
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_8"><span>Note</span></div><p class="">In contrast to the common use of <code>alt</code> attributes in [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>], the <code>ittm:altText</code> attribute content is not intended to be displayed in place of the element if the element is not loaded. The <code>ittm:altText</code> attribute content can however be read and used by assistive technologies.
+        .</p></div>
+      </section>
+			
+		</section>
 
     <section id="region">
       <h3 aria-level="2" role="heading" id="h3_region"><span class="secno">4.6 </span>Region</h3>
@@ -741,7 +799,7 @@
           </li>
         </ol>
 
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_7"><span>Note</span></div><p class="">As specified in [<cite><a class="bibref" href="#bib-TTML1">TTML1</a></cite>], the initial value of <code>tts:opacity</code> is "1.0", the initial
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_9"><span>Note</span></div><p class="">As specified in [<cite><a class="bibref" href="#bib-TTML1">TTML1</a></cite>], the initial value of <code>tts:opacity</code> is "1.0", the initial
         value of <code>tts:showBackground</code> is "always", and the initial value of <code>tts:display</code> is
         "auto"</p></div>
       </section>
@@ -1207,7 +1265,7 @@
         </tbody>
       </table>
 
-      <div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_8"><span>Note</span></div><p class="">As specified in [<cite><a class="bibref" href="#bib-TTML1">TTML1</a></cite>], a <code>#time-offset-with-frames</code> expression is translated to a media time
+      <div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_10"><span>Note</span></div><p class="">As specified in [<cite><a class="bibref" href="#bib-TTML1">TTML1</a></cite>], a <code>#time-offset-with-frames</code> expression is translated to a media time
       M according to M = 3600 · hours + 60 · minutes + seconds + (frames ÷ (<code>ttp:frameRateMultiplier</code> ·
       <code>ttp:frameRate</code>)).</p></div>
     </section>
@@ -1596,9 +1654,19 @@
     <section id="div-element">
       <h3 aria-level="2" role="heading" id="h3_div-element"><span class="secno">6.3 </span><code>div</code> element</h3>
 
-      <p>If a <code>smpte:backgroundImage</code> attribute is applied to a <code>div</code> element, the width and height of the
-      region extent associated with the <code>div</code> element <em class="rfc2119" title="SHALL">SHALL</em> be specified and <em class="rfc2119" title="SHALL">SHALL</em> be equal to the width and height of
-      the image source referenced by the <code>smpte:backgroundImage</code>.</p>
+      <p>If a <code>smpte:backgroundImage</code> attribute is applied to a <code>div</code> element:</p>
+			
+			<ul>
+			<li>
+			the width and height of the region extent associated with the <code>div</code> element <em class="rfc2119" title="SHALL">SHALL</em> be specified and <em class="rfc2119" title="SHALL">SHALL</em> be equal to the width and height of the image source referenced by the <code>smpte:backgroundImage</code>;
+			</li>
+			<li>
+			the <code>metadata</code> element of the <code>div</code> element <em class="rfc2119" title="SHOULD">SHOULD</em> contain an instance of <code>ittm:altText</code> that is a verbatim text  equivalent of the image referenced by the <code>smpte:backgroundImage</code> attribute; and
+			</li>
+			<li>
+			The <code>smpte:backgroundImage</code> attribute <em class="rfc2119" title="SHALL">SHALL</em> reference a complete image that conforms to the PNG image coding as specified in Sections 7.1.1.3 and 15.1 of [<cite><a class="bibref" href="#bib-MHP">MHP</a></cite>]. If a pHYs chunk is present, it <em class="rfc2119" title="SHALL">SHALL</em> indicate square pixels. Note: If no pixel aspect ratio is carried, the default of square pixels is assumed.<br>
+			</li>
+			</ul>
     </section>
 
     <section id="features-1">
@@ -1752,12 +1820,10 @@
           <tr>
             <td><code>#image</code></td>
 
-            <td><code>smpte:backgroundImage</code> <em class="rfc2119" title="MAY">MAY</em> be used. The <code>smpte:backgroundImage</code> attribute <em class="rfc2119" title="SHALL">SHALL</em> reference a
-            complete image that conforms to the PNG image coding as specified in Sections 7.1.1.3 and 15.1 of [<cite><a class="bibref" href="#bib-MHP">MHP</a></cite>]. If a pHYs
-            chunk is present, it <em class="rfc2119" title="SHALL">SHALL</em> indicate square pixels. Note: If no pixel aspect ratio is carried, the default of square
-            pixels is assumed.<br>
+            <td><code>smpte:backgroundImage</code> <em class="rfc2119" title="MAY">MAY</em> be used.<br>
             <code>smpte:backgroundImageHorizontal</code> and <code>smpte:backgroundImageVertical</code> <em class="rfc2119" title="SHALL NOT">SHALL NOT</em> be used.<br>
             <code>smpte:image</code> <em class="rfc2119" title="SHALL NOT">SHALL NOT</em> be used.</td>
+						
           </tr>
         </tbody>
       </table>
@@ -1866,7 +1932,7 @@
         P<sub>n-1</sub> at the presentation time of intermediate synchronic document E<sub>n</sub>, making the latter available for
         display.</p>
 
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_9"><span>Note</span></div><p class="">It is possible for the contents of Presentation Buffer P<sub>n-1</sub> to never be displayed. This can
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_11"><span>Note</span></div><p class="">It is possible for the contents of Presentation Buffer P<sub>n-1</sub> to never be displayed. This can
         happen if Presentation Buffer P<sub>n</sub> is copied twice to Presentation Buffer P<sub>n-1</sub> between two consecutive
         video frame boundaries of the related video object.</p></div>
 
@@ -1899,11 +1965,11 @@
           </tbody>
         </table>
 
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_10"><span>Note</span></div><p class="">BDraw effectively sets a limit on fillings regions - for example, assuming that the root container is
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_12"><span>Note</span></div><p class="">BDraw effectively sets a limit on fillings regions - for example, assuming that the root container is
         ultimately rendered at 1920×1080 resolution, a BDraw of 12 s<sup>-1</sup> would correspond to a fill rate of
         1920×1080×12/s=23.7×2<sup>20</sup>pixels s<sup>-1</sup>.</p></div>
 
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_11"><span>Note</span></div><p class="">IPD effectively sets a limit on the complexity of any given intermediate synchronic document.</p></div>
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_13"><span>Note</span></div><p class="">IPD effectively sets a limit on the complexity of any given intermediate synchronic document.</p></div>
       </section>
 
       <section id="paint-regions" typeof="bibo:Chapter" resource="#paint-regions" rel="bibo:Chapter">
@@ -1915,7 +1981,7 @@
 
         <p>where CLEAR(E<sub>0</sub>) = 0 and CLEAR(E<sub>n | n &gt; 0</sub>) = 1, i.e. the root container in its entirety.</p>
 
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_12"><span>Note</span></div><p class="">To ensure consistency of the Presentation Buffer, a new intermediate synchronic document requires clearing
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_14"><span>Note</span></div><p class="">To ensure consistency of the Presentation Buffer, a new intermediate synchronic document requires clearing
         of the root container.</p></div>
 
         <p>PAINT(E<sub>n</sub>) <em class="rfc2119" title="SHALL">SHALL</em> be the normalized area to be painted for all regions that are used in intermediate synchronic
@@ -2166,7 +2232,7 @@
           </tbody>
         </table>
 
-        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_13"><span>Note</span></div><p class="">NRGA(G<sub>i</sub>) does not take into account glyph decorations (e.g. underline), glyph effects (e.g.
+        <div class="note"><div class="note-title" aria-level="4" role="heading" id="h_note_15"><span>Note</span></div><p class="">NRGA(G<sub>i</sub>) does not take into account glyph decorations (e.g. underline), glyph effects (e.g.
         outline) or actual glyph aspect ratio. An implementation can determine an actual buffer size needs based on worst-case
         glyph size complexity.</p></div>
 
@@ -2247,10 +2313,10 @@
         </tbody>
       </table>
 
-      <div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_14"><span>Note</span></div><p class="">Implementations can use use fonts other than those specified above. Two fonts with equal metrics can have a
+      <div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_16"><span>Note</span></div><p class="">Implementations can use use fonts other than those specified above. Two fonts with equal metrics can have a
       different appearance, but flow identically.</p></div>
 
-      <div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_15"><span>Note</span></div><p class="">proportionalSansSerif is not used in practice for Hebrew and Arabic captions and subtitles.</p></div>
+      <div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_17"><span>Note</span></div><p class="">proportionalSansSerif is not used in practice for Hebrew and Arabic captions and subtitles.</p></div>
     </section>
   </section>
 
@@ -2591,19 +2657,36 @@
       </tbody>
     </table>
   </section>
+	
+	<section class="appendix" id="wcag-applications" typeof="bibo:Chapter" resource="#wcag-applications" rel="bibo:Chapter">
+    <!--OddPage--><h2 aria-level="1" role="heading" id="h2_wcag-applications"><span class="secno">B. </span>WCAG Considerations</h2>
+		
+		<p>This Section <em class="rfc2119" title="SHALL">SHALL</em> apply to applications following the guidelines at [<cite><a class="bibref" href="#bib-WCAG20">WCAG20</a></cite>].</p>
+		
+	<p>
+Guideline 1.1 of [<cite><a class="bibref" href="#bib-WCAG20">WCAG20</a></cite>] recommends that an implementation provide text alternatives for all non-text content. In the context of this specification, this text alternative is intended primarily to support users of the subtitles who cannot see images. Since the images of an Image Profile subtitle document usually represent subtitle or caption text, the guidelines for authoring text equivalent strings given at <span class="sec-no">Images of text</span> of [<cite><a class="bibref" href="#bib-HTML5">HTML5</a></cite>] are appropriate.</p>
+
+	<p>
+Thus, for each subtitle in an Image Profile subtitle document, a text equivalent content in a Text Profile subtitle document <em class="rfc2119" title="SHOULD">SHOULD</em> be written so that it conveys all essential content and fulfills the same function as the corresponding subtitle image. In the context of subtitling and captioning, this content will be (as a minimum) the verbatim equivalent of the image without précis or summarization. However, the author <em class="rfc2119" title="MAY">MAY</em> include extra information to the text equivalent string in cases where styling is applied to the text image with a deliberate connotation, as a <em>functional</em> replacement for the applied style.</p>
+
+<p>For instance, in subtitling and captioning, italics can be used to indicate an off screen speaker context (for example a voice from a radio). An author can choose to include this functional information in the text equivalent; for example, by including the word "Radio: " before the image equivalent text. It should also be noted that images in an Image Profile subtitle document that are intended for use as <em>captions</em>, i.e. intended for a hard of hearing audience, might already include this functional information in the rendered text.</p>
+
+<p>Guideline 1.1 of [<cite><a class="bibref" href="#bib-WCAG20">WCAG20</a></cite>] also recommends that accessible text alternatives must be "programmatically determinable." This means that the text must be able to be read and used by the assistive technologies (and the accessibility features in browsers) that people with disabilities use. It also means that the user must be able to use their assistive technology to find the alternative text (that they can use) when they land on the non-text content (that they can't use).</p>
+
+	</section>
 
   <section class="appendix" id="features-and-extensions" typeof="bibo:Chapter" resource="#features-and-extensions" rel="bibo:Chapter">
-    <!--OddPage--><h2 aria-level="1" role="heading" id="h2_features-and-extensions"><span class="secno">B. </span>Extensions</h2>
+    <!--OddPage--><h2 aria-level="1" role="heading" id="h2_features-and-extensions"><span class="secno">C. </span>Extensions</h2>
 
     <section class="appendix" id="general-2">
-      <h3 aria-level="2" role="heading" id="h3_general-2"><span class="secno">B.1 </span>General</h3>
+      <h3 aria-level="2" role="heading" id="h3_general-2"><span class="secno">C.1 </span>General</h3>
 
       <p>The following sections define extension designations, expressed as relative URIs (fragment identifiers) relative to the
       IMSC 1.0 Extension Namespace base URI.</p>
     </section>
 
     <section class="appendix" id="progressivelydecodable">
-      <h3 aria-level="2" role="heading" id="h3_progressivelydecodable"><span class="secno">B.2 </span>#progressivelyDecodable</h3>
+      <h3 aria-level="2" role="heading" id="h3_progressivelydecodable"><span class="secno">C.2 </span>#progressivelyDecodable</h3>
 
       <p>A TTML transformation processor supports the <code>#progressivelyDecodable</code> feature if it recognizes and is capable
       of transforming values of the <a href="#ttp-progressivelyDecodable"><code>ittp:progressivelyDecodable</code></a>.</p>
@@ -2614,7 +2697,7 @@
     </section>
 
     <section class="appendix" id="aspectratio">
-      <h3 aria-level="2" role="heading" id="h3_aspectratio"><span class="secno">B.3 </span>#aspectRatio</h3>
+      <h3 aria-level="2" role="heading" id="h3_aspectratio"><span class="secno">C.3 </span>#aspectRatio</h3>
 
       <p>A TTML transformation processor supports the <code>#aspectRatio</code> feature if it recognizes and is capable of
       transforming values of the <a href="#ttp-aspectRatio"><code>ittp:aspectRatio</code></a>.</p>
@@ -2624,7 +2707,7 @@
     </section>
 
     <section class="appendix" id="forceddisplay">
-      <h3 aria-level="2" role="heading" id="h3_forceddisplay"><span class="secno">B.4 </span>#forcedDisplay</h3>
+      <h3 aria-level="2" role="heading" id="h3_forceddisplay"><span class="secno">C.4 </span>#forcedDisplay</h3>
 
       <p>A TTML transformation processor supports the <code>#forcedDisplay</code> feature if it recognizes and is capable of
       transforming values of the <a href="#tts-forcedDisplay"><code>itts:forcedDisplay</code></a>.</p>
@@ -2633,18 +2716,30 @@
       support for values of the <a href="#tts-forcedDisplay"><code>itts:forcedDisplay</code></a> attribute.</p>
     </section>
   </section>
-
-
-<section id="references" class="appendix" typeof="bibo:Chapter" resource="#references" rel="bibo:Chapter"><!--OddPage--><h2 aria-level="1" role="heading" id="h2_references"><span class="secno">C. </span>References</h2><section id="normative-references" typeof="bibo:Chapter" resource="#normative-references" rel="bibo:Chapter"><h3 aria-level="2" role="heading" id="h3_normative-references"><span class="secno">C.1 </span>Normative references</h3><dl class="bibliography" about=""><dt id="bib-CLDR">[CLDR]</dt><dd rel="dcterms:requires">Unicode Consortium. <a href="http://cldr.unicode.org">The Common Locale Data Repository Project</a>
+	
+	<section class="appendix" id="alttext">
+      <!--OddPage--><h2 aria-level="1" role="heading" id="h2_alttext"><span class="secno">D. </span>#altText</h2>
+
+      <p>A TTML transformation processor supports the <code>#altText</code> feature if it recognizes and is capable of
+      transforming values of the <a href="#ttm-altText"><code>ittm:altText</code></a> element.</p>
+
+      <p>A TTML presentation processor supports the <code>#forcedDisplay</code> feature if it implements presentation semantic
+      support for values of the <a href="#ttm-altText"><code>ittm:altText</code></a> element.</p>
+    </section>
+  
+
+
+<section id="references" class="appendix" typeof="bibo:Chapter" resource="#references" rel="bibo:Chapter"><!--OddPage--><h2 aria-level="1" role="heading" id="h2_references"><span class="secno">E. </span>References</h2><section id="normative-references" typeof="bibo:Chapter" resource="#normative-references" rel="bibo:Chapter"><h3 aria-level="2" role="heading" id="h3_normative-references"><span class="secno">E.1 </span>Normative references</h3><dl class="bibliography" about=""><dt id="bib-CLDR">[CLDR]</dt><dd rel="dcterms:requires">Unicode Consortium. <a href="http://cldr.unicode.org">The Common Locale Data Repository Project</a>
 </dd><dt id="bib-MHP">[MHP]</dt><dd rel="dcterms:requires">ETSI TS 101 812 V1.3.1, Digital Video Broadcasting (DVB); Multimedia Home
 </dd><dt id="bib-RFC2119">[RFC2119]</dt><dd rel="dcterms:requires">S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key words for use in RFCs to Indicate Requirement Levels</cite></a>. March 1997. Best Current Practice. URL: <a href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
 </dd><dt id="bib-ST2052-1">[ST2052-1]</dt><dd rel="dcterms:requires">SMPTE ST 2052-1, Timed Text Format (SMPTE-TT)
 </dd><dt id="bib-TTML1">[TTML1]</dt><dd rel="dcterms:requires">Glenn Adams, Ed., <a href="http://www.w3.org/TR/ttml1/"><cite>Timed Text Markup Language 1 (TTML1) (Second Edition)</cite></a>, W3C Recommendation, 24 September 2013. URL: <a href="http://www.w3.org/TR/2013/REC-ttml1-20130924/">http://www.w3.org/TR/2013/REC-ttml1-20130924/</a>
 </dd><dt id="bib-UNICODE">[UNICODE]</dt><dd rel="dcterms:requires"><a href="http://www.unicode.org/versions/latest/"><cite>The Unicode Standard</cite></a>. URL: <a href="http://www.unicode.org/versions/latest/">http://www.unicode.org/versions/latest/</a>
+</dd><dt id="bib-WCAG20">[WCAG20]</dt><dd rel="dcterms:requires">Ben Caldwell; Michael Cooper; Loretta Guarino Reid; Gregg Vanderheiden et al. <a href="http://www.w3.org/TR/WCAG20/"><cite>Web Content Accessibility Guidelines (WCAG) 2.0</cite></a>. 11 December 2008. W3C Recommendation. URL: <a href="http://www.w3.org/TR/WCAG20/">http://www.w3.org/TR/WCAG20/</a>
 </dd><dt id="bib-xml-names">[xml-names]</dt><dd rel="dcterms:requires">Tim Bray; Dave Hollander; Andrew Layman; Richard Tobin; Henry Thompson et al. <a href="http://www.w3.org/TR/xml-names"><cite>Namespaces in XML 1.0 (Third Edition)</cite></a>. 8 December 2009. W3C Recommendation. URL: <a href="http://www.w3.org/TR/xml-names">http://www.w3.org/TR/xml-names</a>
-</dd></dl></section><section id="informative-references" typeof="bibo:Chapter" resource="#informative-references" rel="bibo:Chapter"><h3 aria-level="2" role="heading" id="h3_informative-references"><span class="secno">C.2 </span>Informative references</h3><dl class="bibliography" about=""><dt id="bib-CEA-608">[CEA-608]</dt><dd rel="dcterms:references"><a href="http://www.ce.org/Standards/Standard-Listings/R4-3-Television-Data-Systems-Subcommittee/Line-21-Data-Service.aspx">Line-21 Data Services</a>, ANSI/CEA Standard.
+</dd></dl></section><section id="informative-references" typeof="bibo:Chapter" resource="#informative-references" rel="bibo:Chapter"><h3 aria-level="2" role="heading" id="h3_informative-references"><span class="secno">E.2 </span>Informative references</h3><dl class="bibliography" about=""><dt id="bib-CEA-608">[CEA-608]</dt><dd rel="dcterms:references"><a href="http://www.ce.org/Standards/Standard-Listings/R4-3-Television-Data-Systems-Subcommittee/Line-21-Data-Service.aspx">Line-21 Data Services</a>, ANSI/CEA Standard.
 </dd><dt id="bib-CEA-708">[CEA-708]</dt><dd rel="dcterms:references"><a href="http://www.ce.org/Standards/Standard-Listings/R4-3-Television-Data-Systems-Subcommittee/CEA-708-D.aspx">Digital Television (DTV) Closed Captioning</a>, ANSI/CEA Standard.
+</dd><dt id="bib-HTML5">[HTML5]</dt><dd rel="dcterms:references">Robin Berjon; Steve Faulkner; Travis Leithead; Erika Doyle Navara; Edward O'Connor; Silvia Pfeiffer. <a href="http://www.w3.org/TR/html5/"><cite>HTML5</cite></a>. 17 June 2014. W3C Last Call Working Draft. URL: <a href="http://www.w3.org/TR/html5/">http://www.w3.org/TR/html5/</a>
 </dd><dt id="bib-SDPUS">[SDPUS]</dt><dd rel="dcterms:references">World Wide Web Consortium (W3C). <a href="http://www.w3.org/TR/ttml10-sdp-us/">TTML Simple Delivery Profile for Closed Captions (US)</a> (W3C Working Group Note, 05 February 2013)
 </dd><dt id="bib-SUBM">[SUBM]</dt><dd rel="dcterms:references">World Wide Web Consortium (W3C). <a href="http://www.w3.org/Submission/2013/SUBM-ttml-ww-profiles-20130607/">TTML Text and Image Profiles for Internet Media Subtitles and Captions</a> (Member Submission, 07 June 2013)
-</dd><dt id="bib-WCAG20">[WCAG20]</dt><dd rel="dcterms:references">Ben Caldwell; Michael Cooper; Loretta Guarino Reid; Gregg Vanderheiden et al. <a href="http://www.w3.org/TR/WCAG20/"><cite>Web Content Accessibility Guidelines (WCAG) 2.0</cite></a>. 11 December 2008. W3C Recommendation. URL: <a href="http://www.w3.org/TR/WCAG20/">http://www.w3.org/TR/WCAG20/</a>
 </dd></dl></section></section></body></html>
\ No newline at end of file
--- a/ttml-ww-profiles/ttml-ww-profiles.source.html	Mon Jun 16 20:33:15 2014 -0700
+++ b/ttml-ww-profiles/ttml-ww-profiles.source.html	Fri Jul 11 18:43:33 2014 -0700
@@ -86,10 +86,15 @@
       <h3>General</h3>
 
       <p>A subtitle document SHALL NOT conform to the Text and Image Profiles simultaneously.</p>
-
-      <p class='NOTE'>Some applications require the same subtitle/caption content to be available in both text and image form
-      simultaneously (see [[WCAG20]] for instance). For these applications, two distinct subtitle documents, one conforming to the
-      Text Profile and the other conforming to the Image Profile, can be offered.</p>
+			
+			<p>In applications that require subtitle/caption content in image form to be simultaneously available in text form, two distinct subtitle documents, one conforming to the Text Profile and the other conforming to the Image Profile, SHOULD be offered. In addition, the Text Profile subtitle document SHOULD be associated with the Image Profile subtitle document such that, when image content is encountered, assistive technologies have access to its corresponding text form.</p>
+			
+						
+			<p class='note'>The <code>ittm:altText</code> element specified <a href='#ttm-altText'></a> also allows text equivalent string to be associated with an image, e.g. to support indexation of the content and also facilitate quality checking of the document during authoring.</p>
+			
+			
+			<p>Annex <a href='#wcag-applications'></a> specifically discusses this specification in the context of the [[WCAG20]] guidelines.</a>
+
     </section>
 
     <section>
@@ -136,6 +141,16 @@
 
         <tbody>
           <tr>
+            <td>XML</td>
+
+            <td>xml</td>
+
+            <td>http://www.w3.org/XML/1998/namespace</td>
+
+            <td>[[!xml-names]]</td>
+          </tr>
+
+          <tr>
             <td>TT Parameter</td>
 
             <td>ttp</td>
@@ -194,6 +209,16 @@
 
             <td><em>This specification</em></td>
           </tr>
+					
+					<tr>
+            <td>IMSC 1.0 Metadata</td>
+
+            <td>ittm</td>
+
+            <td>http://www.w3.org/ns/ttml/profile/imsc1#metadata</td>
+
+            <td><em>This specification</em></td>
+          </tr>
 
           <tr>
             <td>IMSC 1.0 Extension</td>
@@ -420,7 +445,41 @@
 				
 				<p class='note'>Future versions of [[!TTML1]] might introduce more generic mechanisms for conditional display of content elements.</p>
       </section>
-    </section>
+    
+		  <section id='ttm-altText'>
+        <h4>ittm:altText</h4>
+
+        <p><code>ittm:altText</code> allows an author to provide a text string equivalent for an element, typically an image. This text equivalent MAY be used to support indexation of the content and also facilitate quality checking of the document during authoring.</p>
+				
+			  <p>The <code>ittm:altText</code> element SHALL conform to the following syntax:</p>
+
+        <table class="syntax">
+          <tbody>
+            <tr>
+              <td>
+                <div class="exampleInner">
+                  <pre>
+&lt;ittm:altText
+  xml:id = ID
+  xml:lang = string
+  xml:space = (default|preserve)
+  {any attribute not in the IMSC 1.0 Metadata namespace}&gt;
+  Content: #PCDATA
+&lt;/ittm:altText&gt;
+</pre>
+                </div>
+              </td>
+            </tr>
+          </tbody>
+        </table>
+				
+				<p><a href="#image-profile-constraints"></a> specifies the use of the <code>ittm:altText</code> element with images.</p>
+
+        <p class='note'>In contrast to the common use of <code>alt</code> attributes in [[HTML5]], the <code>ittm:altText</code> attribute content is not intended to be displayed in place of the element if the element is not loaded. The <code>ittm:altText</code> attribute content can however be read and used by assistive technologies.</code>
+        .</p>
+      </section>
+			
+		</section>
 
     <section>
       <h3>Region</h3>
@@ -1302,9 +1361,19 @@
     <section>
       <h3><code>div</code> element</h3>
 
-      <p>If a <code>smpte:backgroundImage</code> attribute is applied to a <code>div</code> element, the width and height of the
-      region extent associated with the <code>div</code> element SHALL be specified and SHALL be equal to the width and height of
-      the image source referenced by the <code>smpte:backgroundImage</code>.</p>
+      <p>If a <code>smpte:backgroundImage</code> attribute is applied to a <code>div</code> element:</p>
+			
+			<ul>
+			<li>
+			the width and height of the region extent associated with the <code>div</code> element SHALL be specified and SHALL be equal to the width and height of the image source referenced by the <code>smpte:backgroundImage</code>;
+			</li>
+			<li>
+			the <code>metadata</code> element of the <code>div</code> element SHOULD contain an instance of <code>ittm:altText</code> that is a verbatim text  equivalent of the image referenced by the <code>smpte:backgroundImage</code> attribute; and
+			</li>
+			<li>
+			The <code>smpte:backgroundImage</code> attribute SHALL reference a complete image that conforms to the PNG image coding as specified in Sections 7.1.1.3 and 15.1 of [[!MHP]]. If a pHYs chunk is present, it SHALL indicate square pixels. Note: If no pixel aspect ratio is carried, the default of square pixels is assumed.<br>
+			</li>
+			</ul>
     </section>
 
     <section>
@@ -1458,12 +1527,10 @@
           <tr>
             <td><code>#image</code></td>
 
-            <td><code>smpte:backgroundImage</code> MAY be used. The <code>smpte:backgroundImage</code> attribute SHALL reference a
-            complete image that conforms to the PNG image coding as specified in Sections 7.1.1.3 and 15.1 of [[!MHP]]. If a pHYs
-            chunk is present, it SHALL indicate square pixels. Note: If no pixel aspect ratio is carried, the default of square
-            pixels is assumed.<br>
+            <td><code>smpte:backgroundImage</code> MAY be used.<br>
             <code>smpte:backgroundImageHorizontal</code> and <code>smpte:backgroundImageVertical</code> SHALL NOT be used.<br>
             <code>smpte:image</code> SHALL NOT be used.</td>
+						
           </tr>
         </tbody>
       </table>
@@ -2299,6 +2366,23 @@
       </tbody>
     </table>
   </section>
+	
+	<section class='appendix' id='wcag-applications'>
+    <h2>WCAG Considerations</h2>
+		
+		<p>This Section SHALL apply to applications following the guidelines at [[!WCAG20]].</p>
+		
+	<p>
+Guideline 1.1 of [[!WCAG20]] recommends that an implementation provide text alternatives for all non-text content. In the context of this specification, this text alternative is intended primarily to support users of the subtitles who cannot see images. Since the images of an Image Profile subtitle document usually represent subtitle or caption text, the guidelines for authoring text equivalent strings given at <span class='sec-no'>Images of text</span> of [[HTML5]] are appropriate.</p>
+
+	<p>
+Thus, for each subtitle in an Image Profile subtitle document, a text equivalent content in a Text Profile subtitle document SHOULD be written so that it conveys all essential content and fulfills the same function as the corresponding subtitle image. In the context of subtitling and captioning, this content will be (as a minimum) the verbatim equivalent of the image without précis or summarization. However, the author MAY include extra information to the text equivalent string in cases where styling is applied to the text image with a deliberate connotation, as a <em>functional</em> replacement for the applied style.</p>
+
+<p>For instance, in subtitling and captioning, italics can be used to indicate an off screen speaker context (for example a voice from a radio). An author can choose to include this functional information in the text equivalent; for example, by including the word "Radio: " before the image equivalent text. It should also be noted that images in an Image Profile subtitle document that are intended for use as <em>captions</em>, i.e. intended for a hard of hearing audience, might already include this functional information in the rendered text.</p>
+
+<p>Guideline 1.1 of [[!WCAG20]] also recommends that accessible text alternatives must be "programmatically determinable." This means that the text must be able to be read and used by the assistive technologies (and the accessibility features in browsers) that people with disabilities use. It also means that the user must be able to use their assistive technology to find the alternative text (that they can use) when they land on the non-text content (that they can't use).</p>
+
+	</section>
 
   <section class='appendix' id='features-and-extensions'>
     <h2>Extensions</h2>
@@ -2341,5 +2425,16 @@
       support for values of the <a href="#tts-forcedDisplay"><code>itts:forcedDisplay</code></a> attribute.</p>
     </section>
   </section>
+	
+	<section class='appendix'>
+      <h3>#altText</h3>
+
+      <p>A TTML transformation processor supports the <code>#altText</code> feature if it recognizes and is capable of
+      transforming values of the <a href="#ttm-altText"><code>ittm:altText</code></a> element.</p>
+
+      <p>A TTML presentation processor supports the <code>#forcedDisplay</code> feature if it implements presentation semantic
+      support for values of the <a href="#ttm-altText"><code>ittm:altText</code></a> element.</p>
+    </section>
+  </section>
 </body>
 </html>