From 9b62fffa6a355cd893c46182483ecedb0c695d9c Mon Sep 17 00:00:00 2001
From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Thu, 29 Aug 2024 16:15:58 +0100
Subject: [PATCH] Add section about mapping from TTML to the DAPT data model
 (#216)
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* wip commit

* More wip changes

* Fix broken reference to unrecognised attribute section
* Mention design goal of future compatibility
* Add section on computed attribute values
* Add TODO for validation warnings and errors

* Add example unexpected attributes

* More TTML to DAPT model considerations

* Make Data model diagram clearly informative
* Add links
* Put explanatory text around examples into a single example `<aside>` including the example XML
* Add rule for non-rejection of Script Events if they contain unrecognised attributes
* Add the results of applying the rules to the div and p example
* Add example showing the effect of attribute computation
* Add section about retaining unrecognised vocabulary
* Add section about validation warnings and errors

* Adjust processor requirement to ignore unrecognised attributes

Clarify that attribute computation needs to happen before anything is ignored.

* Move new section to after Constraints

* WIP changes

* Rework introduction to Mapping from TTML to DAPT section.
  * Make it normative.
* Make most subsections informative, but make the normative ones use normative keywords, e.g. the one about div and p structural handling.
* Add section for document conformance claims handling

* Handle unrecognised vocabulary better

As discussed in https://github.com/w3c/dapt/pull/216#issuecomment-2077620555:
* Define restriction on `ttp:contentProfiles` values within the section on contentProfiles
* Define and use the term "foreign vocabulary"
* Advise retention of unsupported foreign vocabulary in `<metadata>` elements
* Require pruning of unsupported vocabulary outside `<metadata>` elements
* Provide a documented path to allowing foreign vocabulary to be defined and supported
* Note that structural changes could lead to loss of foreign vocabulary if the `<metadata>` element to which it is associated is removed.

* Improve section heading for Proprietary Metadata

Because it now also describes how to insert foreign vocabulary

* Mark "Using computed attribute values" as informative

It contains no normative keywords.

* scriptEventMapping extension, address Respec changes

Add extension feature `#scriptEventMapping` and make it optional

Address recent changes to Respec to fix up tables that used to have `class="simple"` and to make the spec work in dark mode.

* Address review feedback

* minor editorial wording tweak

* Add link to issue #233

Also fix broken HTML formatting with `<ul>` inside `<p>` where it doesn't belong.

* Move note to §6.1

* Allow for DAPT documents with other content profiles

* Warn not to put data in metadata if it depends on the document contents

* Define Unrecognised vocabulary

* Address review feedback

Remove unnecessary sentence; define MUST before SHOULD.

* Split SHOULD requirement for presentation processors to ignore elements and attributes.

* Rewrite first section of Mapping from TTML to the DAPT Data Model

Based on @cconcolato 's review comments, with small editorial adjustments.

* Attempt to address feedback

Rename "Document conformance claims on output", mark as informative; move the section about processor behaviour into a new normative section "Not supporting features excluded by the content profile".

Some wording edits too.

* Use xml:space as an example of non-DAPT data model attributes on div

* Make processorProfiles generic like contentProfiles

* Change pruning/preservation rules to ref unrecognised vocabulary

* Address review feedback

Restructure the Unrecognised Elements and Attributes section to split unrecognised vocabulary sections from foreign vocabulary sections.

Rename Profile Designator section to be plural.

Delete informative section that repeats normative requirements elsewhere, re avoiding unverified profile conformance signalling.

* Address review feedback

Define foreign vocabulary before referencing it.

Put considerations for transformation and validation processors into a separate subsection of §6.

* Presentation processors should ignore unrecognised vocabulary

* Clarify sentence about namespace mutability.

* Reword validation warnings section

Remove "optional" category.

* Improve sentence structure re TTML pruning

* Positively identify TTML to DAPT model mappings

* Explicitly state that nested divs are allowed

Makes the data model section match the requirements of the TTML -> DAPT model parsing section.

* Clarify that a DAPT Document is a "timed text content document instance"

Closes #234.

* Introduce the root `<tt>` element as a note

Rather than assuming that the reader already knows exactly what a TTML2 timed text content document instance looks like.

* Tidy the definitions of the TTML representation of DAPT Scripts

* Be explicit about the need for `<head>`, `<metadata>` and `<body>` elements.
* Specify the path of Script Events and Text objects, for convenience.
* Be clear that the `daptm:langSrc` attribute on a `<p>` element represents the Text Language Source (weird that we didn't before).
* State that no semantic is defined for `<div>` elements that are not Script Events.
* Now that there is explicit permission to have nested `<div>`s, allow for that in the section about handling `<div>` and `<p>` elements, i.e. they are not just a theoretical construct allowed in TTML, but they are explicitly permitted in DAPT too.

* Address review feedback
---
 examples/non-dapt-div-with-begin-and-lang.xml |  14 +
 examples/non-dapt-divs.xml                    |  22 +
 index.html                                    | 695 ++++++++++++++----
 profiles/dapt-content-profile.xml             |   1 +
 profiles/dapt-processor-profile.xml           |   1 +
 5 files changed, 587 insertions(+), 146 deletions(-)
 create mode 100644 examples/non-dapt-div-with-begin-and-lang.xml
 create mode 100644 examples/non-dapt-divs.xml

diff --git a/examples/non-dapt-div-with-begin-and-lang.xml b/examples/non-dapt-div-with-begin-and-lang.xml
new file mode 100644
index 0000000..2529725
--- /dev/null
+++ b/examples/non-dapt-div-with-begin-and-lang.xml
@@ -0,0 +1,14 @@
+<tt ... xml:lang="en">
+    <body>
+        <div xml:id="d1" begin="00:01:00" end="00:01:10">
+            <!-- Script Event beginning at 1 minute, duration 10 seconds -->
+            <p> <!-- This is a Text, language "en" --> </p>
+        </div>
+        <div begin="00:10:00" xml:lang="fr"> <!-- div that is not a Script Event -->
+            <div xml:id="d2" begin="00:01:00" end="00:01:10">
+                <!-- Script Event beginning at 11 minutes, duration 10 seconds -->
+                <p> <!-- This is a Text, language "fr" --> </p>
+            </div>
+        </div>
+    </body>
+</tt>
diff --git a/examples/non-dapt-divs.xml b/examples/non-dapt-divs.xml
new file mode 100644
index 0000000..8f0b78a
--- /dev/null
+++ b/examples/non-dapt-divs.xml
@@ -0,0 +1,22 @@
+<body>
+    <div xml:id="d1"> <!-- This is a Script Event -->
+        <p> <!-- This is a Text --> </p>
+    </div>
+    <div> <!-- This cannot be a Script Event because it has no xml:id -->
+        <p> <!-- Would be a Text if its parent were a Script Event --> </p>
+    </div>
+    <div> <!-- div parent of another div -->
+        <div xml:id="d2"> <!-- Possibly a Script Event --></div>
+    </div>
+    <div> <!-- double layer of nesting -->
+        <div>
+            <div xml:id="d3" begin="..." end="..." xml:lang="ja" foo:bar="baz">
+                <!-- A Script Event with possibly unexpected attributes -->
+            </div>
+        </div>
+    </div>
+    <div xml:id="d4_1"> <!-- mixed div and p children -->
+        <div xml:id="d4_2"> <!-- This possible Script Event has a sibling <p> --> </div>
+        <p> <!-- Possible Text, but not if its parent is not a Script Event --> </p>
+    </div>
+</body>
diff --git a/index.html b/index.html
index 3b35b2c..f620074 100755
--- a/index.html
+++ b/index.html
@@ -2,6 +2,7 @@
 <html>
   <head>
     <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+    <meta name="color-scheme" content="light dark">
     <title>Dubbing and Audio description Profiles of TTML2</title>
     <script defer src="https://www.w3.org/Tools/respec/respec-w3c" class="remove"></script>
     <script class="remove">
@@ -68,20 +69,86 @@
     };
     </script>
   <style>
-table.coldividers td + td { border-left:1px solid gray; }
+    @media (prefers-color-scheme: dark) {
+      .data tr:nth-child(even) {
+        background: #444444;
+      }
+      span.label.required::before, span.label.required::after {
+        color: black;
+      }
+      span.optional {
+        color: black;
+        background-color: #FFFF50;
+        border-color: #f0f6ff;
+      }
+      span.permitted {
+        color: black;
+        background-color: #50FF50;
+      }
+      span.prohibited {
+        color: black;
+        background-color: #FF5F5F;
+      }
+      span.permitted-deprecated {
+        color: black;
+        background-color: #FFC000;
+      }
+      span.required {
+        color: black;
+        background-color: white;
+      }
+      img.fingerprint, svg {
+        filter: invert(100%);
+      }
+      div.exampleInner {
+        background-color: #282c34;
+      }
+    }
+    @media (prefers-color-scheme: light) {
+      .data tr:nth-child(even) {
+        background: #f0f6ff;
+      }
+      span.label.required::before, span.label.required::after {
+        color: white;
+      }
+      span.optional {
+        color: black;
+        background-color: #FFFF50;
+        border-color: #444444;
+      }
+      span.permitted {
+        color: black;
+        background-color: #50FF50;
+      }
+      span.prohibited {
+        color: black;
+        background-color: #FF5F5F;
+      }
+      span.permitted-deprecated {
+        color: black;
+        background-color: #FFC000;
+      }
+      span.required {
+        color: white;
+        background-color: black;
+      }
+      div.exampleInner {
+        background-color: #fafafa;
+      }
+    }
+  table.coldividers td + td { border-left:1px solid gray; }
   table.syntax { border: 0px solid black; width: 85%; border-collapse: collapse }
   table.syntax caption { font-weight: bold; text-align: left; padding-bottom: 0.5em }
   table.syntax th { border: 0px solid black; text-align: left }
   table.syntax td { border: 0px solid black }
   table.syntax div { background-color: #ffffc8 }
   table#table-features-and-extensions tbody tr td:nth-child(2) { text-align: center;}
-  div.exampleInner { background-color: #fafafa;
-                   border-top-width: 4px;
+  div.exampleInner { border-top-width: 4px;
                    border-top-style: double;
                    border-top-color: #d3d3d3;
+                   border-bottom-color: #d3d3d3;
                    border-bottom-width: 4px;
                    border-bottom-style: double;
-                   border-bottom-color: #d3d3d3;
                    padding: 4px; margin: 0em }
   ul.short-list { margin: 0; padding-left: 0; list-style-position: inside;}
   .equation {text-indent: 10%;}
@@ -117,35 +184,15 @@
   }
   span.label.required::before, span.label.required::after {
     font-weight: bold;
-    color: white;
     content: "\00A0!!\00A0";
   }
   span.label::after {
     content: "\00A0";
   }
   span.optional {
-    color: black;
-    background-color: #FFFF50;
-    border-color: #444444;
     border-style: solid;
     border-width: 1px;
   }
-  span.permitted {
-    color: black;
-    background-color: #50FF50;
-  }
-  span.prohibited {
-    color: black;
-    background-color: #FF5F5F;
-  }
-  span.permitted-deprecated {
-    color: black;
-    background-color: #FFC000;
-  }
-  span.required {
-    color: white;
-    background-color: black;
-  }
   figure svg {
     max-width: max-content !important;
   }
@@ -537,10 +584,10 @@ <h2>DAPT Data Model and corresponding TTML syntax</h2>
       <a>Shared properties</a> are shown in italics.
       All other conventions in the diagram are as per [[?uml]].
     </p>
-    <figure id="fig-class-diagram">
+    <figure id="fig-class-diagram" class="informative">
       <div data-include="figures/class-diagram.svg"></div>
       <figcaption>
-          Class diagram showing main entities in the DAPT data model.
+          (Informative) Class diagram showing main entities in the DAPT data model.
       </figcaption>
     </figure>
     <p class="issue" data-number="116"></p>
@@ -552,10 +599,15 @@ <h3>DAPT Script</h3>
           It has properties and objects defined in the following sections:
           <a>Represents</a>, <a>Script Type</a>, <a>Default Language</a>, <a>Text Language Source</a>, <a>Script Events</a>
           and, for <a>Dubbing Scripts</a>, <a>Characters</a>.</p>
-        <p>A <dfn>DAPT Document</dfn> is a TTML <a>Document Instance</a> representing a <a>DAPT Script</a>.
-          A <a>DAPT Document</a> has the structure and constraints defined in the following sections.</p>
+        <p>A <dfn>DAPT Document</dfn> is a [[TTML2]] <a>timed text content document instance</a> representing a <a>DAPT Script</a>.
+          A <a>DAPT Document</a> has the structure and constraints defined in this and the following sections.</p>
+        <p class="note">
+          A [[TTML2]] <a>timed text content document instance</a> has
+          a root <code>&lt;tt&gt;</code> element
+          in the TT namespace.
+        </p>
 
-          <section>
+        <section>
           <h4>Represents</h4>
           <p>The <dfn>Represents</dfn> property is a mandatory property of a <a>DAPT Script</a> which
             indicates which components of the <a>related media object</a>
@@ -770,12 +822,24 @@ <h4>Script Type</h4>
 
         <section>
           <h4>Script Events</h4>
-          <p>A <a>DAPT Script</a> MAY contain zero or more <a>Script Event</a> objects, each corresponding to dialogue, on screen text, or descriptions for a given time interval.</p>
+          <p>A <a>DAPT Script</a> MAY contain zero or more <a>Script Event</a> objects,
+            each corresponding to dialogue, on screen text, or descriptions for a given time interval.</p>
+
+          <p>If any <a>Script Events</a> are present, the <a>DAPT Document</a> MUST have
+            one <code>&lt;body&gt;</code> element child of the <code>&lt;tt&gt;</code> element.</p>
         </section>
 
         <section>
           <h4>Characters</h4>
           <p>A <a>DAPT Script</a> MAY contain zero or more <a>Character</a> objects, each describing a character that can be referenced by a <a>Script Event</a>.</p>
+
+          <p>If any <a>Character</a> objects are present, the <a>DAPT Document</a> MUST have
+            one <code>&lt;head&gt;</code> element child of the <code>&lt;tt&gt;</code> element,
+            and that <code>&lt;head&gt;</code> element MUST have
+            at least one <code>&lt;metadata&gt;</code> element child.</p>
+
+          <p class="note">It is good practice to locate all the <a>Character</a> objects within
+            a single <code>&lt;metadata&gt;</code> element parent.</p>
         </section>
 
         <section>
@@ -901,7 +965,7 @@ <h3>Character</h3>
 
           <li>All <code>&lt;ttm:agent&gt;</code> elements SHOULD be contained in the first <code>&lt;metadata&gt;</code> element in the <code>&lt;head&gt;</code> element.
             <div class="note">There can be multiple <code>&lt;metadata&gt;</code> elements in the <code>&lt;head&gt;</code> element,
-            for example to include <a href="#proprietary-metadata">proprietary metadata</a>
+            for example to include <a href="#proprietary-metadata-and-foreign-vocabulary">proprietary metadata</a>
             but the above recommends that only one is used to define the characters.</div>
             <aside class="ednote">The group is considering updating the rule(s) around which metadata element
             is used to carry DAPT information. The group would like to balance simplicity of implementation
@@ -912,7 +976,7 @@ <h3>Character</h3>
             The group welcomes feedback from implementers and users."</aside>
           </li>
         </ul>
-        <aside class="note">As indicated in [[[#foreign-elements-and-attributes]]], <code>ttm:agent</code>
+        <aside class="note">As indicated in [[[#unrecognised-elements-and-attributes]]], <code>ttm:agent</code>
         elements can have foreign attributes and elements. This can be used to provide additional, proprietary
         character information.</aside>
 
@@ -921,54 +985,65 @@ <h3>Character</h3>
 
       <section>
         <h3>Script Event</h3>
-        <p>A <dfn>Script Event</dfn> object represents dialogue, on screen text or audio descriptions to be spoken and has the following properties:
-          <ul>
-            <li>A mandatory <dfn>Script Event Identifier</dfn> which is unique in the <a>script</a></li>
-            <li>An optional <a>Begin</a> property and an optional <a>End</a> and an optional <a>Duration</a> property
-              that together define the <a>Script Event</a>'s time interval in the programme timeline
-              <p class="note">Typically <a>Script Events</a> do not overlap in time. However, there can be cases where they do, e.g. in <a>Dubbing Scripts</a> when different <a>Characters</a> speak different text at the same time.</p>
-            </li>
-            <li>An optional <a>Script Event Type</a> used to identify the type of event (e.g. dialogue, on screen text) in <a>Dubbing Scripts</a>.</li>
-            <li>Zero or more <a>Character Identifiers</a> indicating the <a>Characters</a> involved in this <a>Script Event</a>.
-              <p class="note">While typically, a <a>Script Event</a> corresponds to one single <a>Character</a>,
-                there are cases where multiple <a>characters</a> can be associated with a <a>Script Event</a>.
-                This is when all <a>Characters</a> speak the same text at the same time.</p>
-              <p class="note">In a <a>transcript</a>, when the event corresponds to in-image content,
-                for example an <a>audio description</a>, no <a>Character Identifier</a> is needed.
-                However it may be helpful in a <a>Pre-recording Script</a> or an <a>As-recorded Script</a> context
-                to indicate a <a>Character</a> signifying who voices the recording.</p>
-            </li>
-            <li><p>Zero or more <a>Text</a> objects, each being either <a>Original</a> or <a>Translation</a>.</p>
-              <p class="note">A <a>Script Event</a> with no <a>Text</a> objects can be created as part
-                of an initial phase of authoring, in workflows where it is helpful
-                to block out the time intervals during which some content could be present.
-                For example, an empty <a>Script Event</a> with <a>timing properties</a>
-                can be created to identify an opportunity for creating an audio description.
-                See also <a data-cite="DAPT-REQS#identify-key-times-in-programme-dialog-mark-gaps-process-step-1">[DAPT-REQS] Process Step 1</a>.</p>
-              <p class="note">Empty <a>Text</a> objects, i.e. ones that have no text content,
-                can be used to indicate explicitly that there is no text content.
-                It is recommended that empty <a>Text</a> objects are not used as a workflow placeholder to indicate incomplete work.</p></li>
-            <li>zero or more <a>Script Event Description</a> objects, each being a human-readable description of the <a>Script Event</a>.</li>
-            <li>an optional <a>On Screen</a> property, which is an annotation indicating the position of the subject (e.g. a <a>character</a>) of the <a>Script Event</a></li>
-            <li>Zero or more <a>Mixing Instruction</a> objects used to adjust playback of the programme audio during the <a>Script Event</a>.</li>
-          </ul>
-        </p>
+        <p>A <dfn>Script Event</dfn> object represents dialogue, on screen text or audio descriptions to be spoken and has the following properties:</p>
+        <ul>
+          <li>A mandatory <dfn>Script Event Identifier</dfn> which is unique in the <a>script</a></li>
+          <li>An optional <a>Begin</a> property and an optional <a>End</a> and an optional <a>Duration</a> property
+            that together define the <a>Script Event</a>'s time interval in the programme timeline
+            <p class="note">Typically <a>Script Events</a> do not overlap in time.
+              However, there can be cases where they do,
+              e.g. in <a>Dubbing Scripts</a> when different <a>Characters</a> speak different text at the same time.</p>
+          </li>
+          <li>An optional <a>Script Event Type</a> used to identify the type of event (e.g. dialogue, on screen text) in <a>Dubbing Scripts</a>.</li>
+          <li>Zero or more <a>Character Identifiers</a> indicating the <a>Characters</a> involved in this <a>Script Event</a>.
+            <p class="note">While typically, a <a>Script Event</a> corresponds to one single <a>Character</a>,
+              there are cases where multiple <a>characters</a> can be associated with a <a>Script Event</a>.
+              This is when all <a>Characters</a> speak the same text at the same time.</p>
+            <p class="note">In a <a>transcript</a>, when the event corresponds to in-image content,
+              for example an <a>audio description</a>, no <a>Character Identifier</a> is needed.
+              However it may be helpful in a <a>Pre-recording Script</a> or an <a>As-recorded Script</a> context
+              to indicate a <a>Character</a> signifying who voices the recording.</p>
+          </li>
+          <li><p>Zero or more <a>Text</a> objects, each being either <a>Original</a> or <a>Translation</a>.</p>
+            <p class="note">A <a>Script Event</a> with no <a>Text</a> objects can be created as part
+              of an initial phase of authoring, in workflows where it is helpful
+              to block out the time intervals during which some content could be present.
+              For example, an empty <a>Script Event</a> with <a>timing properties</a>
+              can be created to identify an opportunity for creating an audio description.
+              See also <a data-cite="DAPT-REQS#identify-key-times-in-programme-dialog-mark-gaps-process-step-1">[DAPT-REQS] Process Step 1</a>.</p>
+            <p class="note">Empty <a>Text</a> objects, i.e. ones that have no text content,
+              can be used to indicate explicitly that there is no text content.
+              It is recommended that empty <a>Text</a> objects are not used as a workflow placeholder to indicate incomplete work.</p></li>
+          <li>zero or more <a>Script Event Description</a> objects, each being a human-readable description of the <a>Script Event</a>.</li>
+          <li>an optional <a>On Screen</a> property, which is an annotation indicating the position of the subject (e.g. a <a>character</a>) of the <a>Script Event</a></li>
+          <li>Zero or more <a>Mixing Instruction</a> objects used to adjust playback of the programme audio during the <a>Script Event</a>.</li>
+        </ul>
+        
+        <p>A <a>Script Event</a> is represented in a <a>DAPT Document</a> at the path
+        <code>/tt/head/body//div</code>,
+        with the following structure and constraints:</p>
+
+        <p class="issue" data-number="233"></p>
 
-        <p>A <a>Script Event</a> is represented in a <a>DAPT Document</a> by the following structure and constraints:
+        <ul>
+          <li>There MAY be any number of nested <code>&lt;div&gt;</code> element ancestors
+          in the path between the <code>&lt;body&gt;</code> element and
+          the <code>&lt;div&gt;</code> element corresponding to the <a>Script Event</a>.
+          No further semantic is defined for such elements.</li>
+          <li>There MUST be one <code>&lt;div&gt;</code> element corresponding to the <a>Script Event</a>,
+            with the following constraints:
           <ul>
-            <li>There MUST be one <code>&lt;div&gt;</code> element, with the following constraints:
-            <ul>
-              <li>The <code>xml:id</code> attribute MUST be present containing the <a>Script Event Identifier</a>.</li>
-              <li>
-                <p>The <code>begin</code>, <code>end</code> and <code>dur</code> attributes represent respectively the <a>Begin</a>, <a>End</a> and <a>Duration</a> of the <a>Script Event</a>.</p>
-                <p>The <code>begin</code> and <code>end</code> attributes SHOULD be present.
-                  The <code>dur</code> attribute MAY be present.</p>
-                <p class="note">See <a href="#timing-properties"></a> for additional notes on timing properties.</p>
-              </li>
-              <li>The <code>ttm:agent</code> attribute MAY be present and if present,
-                MUST contain a reference to each <code>ttm:agent</code> attribute that represents an associated <a>Character</a>.
+            <li>The <code>xml:id</code> attribute MUST be present containing the <a>Script Event Identifier</a>.</li>
+            <li>
+              <p>The <code>begin</code>, <code>end</code> and <code>dur</code> attributes represent respectively the <a>Begin</a>, <a>End</a> and <a>Duration</a> of the <a>Script Event</a>.</p>
+              <p>The <code>begin</code> and <code>end</code> attributes SHOULD be present.
+                The <code>dur</code> attribute MAY be present.</p>
+              <p class="note">See <a href="#timing-properties"></a> for additional notes on timing properties.</p>
+            </li>
+            <li>The <code>ttm:agent</code> attribute MAY be present and if present,
+              MUST contain a reference to each <code>ttm:agent</code> attribute that represents an associated <a>Character</a>.
               <aside class="note">Multiple references are specified using a space-separated list.</aside>
-          <pre class="example">
+              <pre class="example">
 ...
 &lt;div xml:id=&quot;event_1&quot;
      begin=&quot;9663f&quot; end=&quot;9682f&quot; 
@@ -976,14 +1051,15 @@ <h3>Script Event</h3>
 ...
 &lt;/div&gt;
 ...
-          </pre>
-              </li>
-              <li>It MAY contain zero or more <code>&lt;p&gt;</code> elements representing each <a>Text</a> object.</li>
-              <li>It MAY contain a <code>&lt;metadata&gt;</code> element representing the <a>On Screen</a> property.</li>
-            </ul>
+              </pre>
             </li>
+            <li>It MAY contain zero or more <code>&lt;p&gt;</code> elements representing each <a>Text</a> object.</li>
+            <li>It MAY contain a <code>&lt;metadata&gt;</code> element representing the <a>On Screen</a> property.</li>
+            <li>It MUST NOT contain any <code>&lt;div&gt;</code> element children.</li>
           </ul>
-        </p>
+          </li>
+        </ul>
+        
         </section>
 
         <section>
@@ -1011,7 +1087,8 @@ <h4>Text</h4>
           <p>A <a>Text</a> object may be styled.</p>
           <p>Zero or more <a>Mixing Instruction</a> objects used to modify the programme audio during the <a>Text</a> MAY be present.
           </p>
-          <p>A <a>Text</a> object is represented in a <a>DAPT Document</a> by a <code>&lt;p&gt;</code> element with the following constraints:</p>
+          <p>A <a>Text</a> object is represented in a <a>DAPT Document</a> by a <code>&lt;p&gt;</code> element at the path
+            <code>/tt/head/body//div/p</code>, with the following constraints:</p>
             <ul>
               <li>The <a>Text</a> of the <a>Script Event</a> is represented by the character content
               of the <code>&lt;p&gt;</code> element and of all of its <code>&lt;span&gt;</code> descendant elements,
@@ -1029,8 +1106,9 @@ <h4>Text</h4>
                   Similarly metadata can be added using attributes or <code>&lt;metadata&gt;</code> elements.</aside>
               </li>
               <li>The <code>&lt;p&gt;</code> element SHOULD have a <a><code>daptm:langSrc</code></a> attribute
-                indicating whether the <a>Text</a> is <a>Original</a> or a <a>Translation</a> and if its
-                source had an inherent language.
+                representing the <a>Text</a> object's <a>Text Language Source</a>,
+                that is, indicating whether the <a>Text</a> is <a>Original</a> or a <a>Translation</a> and
+                if its source had an inherent language.
                 <aside class="note">
                   <p>If a <code>&lt;p&gt;</code> element omits the <a><code>daptm:langSrc</code></a> attribute
                     then its computed value is derived by inheritance from its parent element,
@@ -1168,7 +1246,7 @@ <h4>Text Language Source</h4>
           </ul>
           <p class="note">An example of the usage of <a>Text Language Source</a> in a document is present in the <a>Text</a> section.</p>
           <aside class="example">
-            <table class="simple">
+            <table class="data">
               <caption>Table enumerating example values of the <code>xml:lang</code> and
                 <a><code>daptm:langSrc</code></a> attributes for different <a>Original</a> transcript sources and
                 their inherent languages.
@@ -1734,39 +1812,113 @@ <h3>Document Encoding</h3>
             for processing, in which case the serialisation requirements do not apply.</p>
       </section>
       <section>
-        <h3>Foreign Elements and Attributes</h3>
-        <p>
-          A <a>DAPT Document</a> MAY contain elements and attributes that are neither specifically permitted nor forbidden by a profile.
-        </p>
-        <p class ="note">
-          <a>DAPT Documents</a> remain subject to the content conformance requirements specified at Section 3.1 of [[TTML2]].
-          In particular, a <a>DAPT Document</a> can contain elements and attributes not in any TT namespace, i.e. in foreign namespaces, since such elements and attributes are pruned by the algorithm at Section 4 of [[TTML2]] prior to evaluating content conformance.
+        <h3>Processing of unrecognised or foreign elements and attributes</h3>
+        <p>The requirements in this section are intended to facilitate forwards and backwards compatibility,
+          specifically to permit:
         </p>
-        <p class ="note">
-          For validation purposes it is good practice to define and use a content specification for all foreign namespace elements and attributes used within a <a>DAPT Document</a>.
-        </p>
-        <p>
-          A <a>transformation processor</a> SHOULD preserve such elements or attributes whenever possible.
-        </p>
-        <p class="ednote">Do we need to say that a <a>presentation processor</a> may ignore foreign vocab?</p>
+        <ul>
+          <li>DAPT processors targeted at one version of the specification to process <a>DAPT documents</a> that
+            include vocabulary or semantics defined in future versions,
+            albeit without supporting the later features;</li>
+          <li>DAPT processors targeted at one version of the specification to process <a>DAPT documents</a>
+            authored for an earlier version with similar or identical behaviour to a DAPT processor
+            targeted at that earlier version.</li>
+        </ul>
+        <p>A <a>DAPT document</a> that conforms to more than one version of
+          the specification could specify conformance to multiple DAPT <a>content profiles</a>.</p>
+        <section id="unrecognised-elements-and-attributes">
+          <h4>Unrecognised vocabulary</h4>
+          <p><dfn>Unrecognised vocabulary</dfn> is the set of elements and attributes that are
+            not associated with <a href="#disposition-of-features-and-extensions">features</a> that the processor supports.</p>
+          <p>A <a>transformation processor</a> MUST prune <a>unrecognised vocabulary</a> that is
+            neither an attribute nor a descendant of
+            a <code>&lt;metadata&gt;</code> element.</p>
+          <p>A <a>transformation processor</a> SHOULD preserve <a>unrecognised vocabulary</a> that is
+            either an attribute or a descendant of
+            a <code>&lt;metadata&gt;</code> element.</p>
+          <p class="note">See also <a href="#ttp-contentprofiles"></a> which prohibits the signalling of profile
+          conformance to profiles that the <a>transformation processor</a> does not support.</p>
+          <p>
+            After <a href="#using-computed-attribute-values">attribute value computation</a>,
+            a <a>presentation processor</a> SHOULD ignore <a>unrecognised vocabulary</a>.
+          </p>
+          <p class="note">
+            The above constraint is specified as being after attribute value computation because it is possible
+            that an implementation recognises and supports attributes present only on particular elements,
+            for example those corresponding to the DAPT data model.
+            As described in <a href="#using-computed-attribute-values"></a> it is important that processor implementations
+            do not ignore such attributes when present on other elements.
+          </p>
+        </section>
+        <section>
+          <h4>Special considerations for foreign vocabulary</h4>
+          <p><dfn>Foreign vocabulary</dfn> is the subset of <a>unrecognised vocabulary</a> that consists of
+            those elements and attributes whose namespace
+            is not one of the namespaces listed in <a href="#namespaces"></a> and
+            those attributes in the global namespace that are not otherwise defined in DAPT or in [[TTML2]].</p>
+          <p>
+            A <a>DAPT Document</a> MAY contain <a>foreign vocabulary</a> that is neither specifically permitted nor forbidden
+            by the profiles signalled in <a>ttp:contentProfiles</a>.
+          </p>
+          <p class ="note">
+            For validation purposes it is good practice to define and use
+            a specification for all <a>foreign vocabulary</a> used within a <a>DAPT Document</a>,
+            for example a <a>content profile</a>.
+          </p>
+        </section>
 
         <section>
-          <h4>Proprietary Metadata</h4>
+          <h4>Proprietary Metadata and Foreign Vocabulary</h4>
           <p>Many dubbing and <a>audio description</a> workflows permit annotation of <a>Script Events</a> or documents with proprietary metadata.
             Metadata vocabulary defined in this specification or in [[TTML2]] MAY be included.
-            Additional vocabulary in other namespaces MAY also be included.</p>
-          <p class="note">It is possible to add information such as the title of the programme using [[TTML2]] constructs.</p>
-          <pre class="example"
-            data-include="examples/metadata-TTML2.xml"
-            data-include-format="text">
-          </pre>
-          <p class="note">It is possible to add workflow-specific information using a foreign namespace.
-            In the following example, a fictitious namespace <code>vendorm</code> from an "example vendor" is used
-            to provide document-level information not defined by DAPT.</p>
-          <pre class="example"
-            data-include="examples/metadata-proprietary.xml"
-            data-include-format="text">
-          </pre>
+            <a>Foreign vocabulary</a> MAY also be included,
+            either as attributes of <code>&lt;metadata&gt;</code> elements or
+            as descendant elements of <code>&lt;metadata&gt;</code> elements.</p>
+          <div class="note">
+            <p>It is possible to add information such as the title of the programme using [[TTML2]] constructs.</p>
+            <pre class="example"
+              data-include="examples/metadata-TTML2.xml"
+              data-include-format="text">
+            </pre>
+          </div>
+          <div class="note">
+            <p>It is possible to add workflow-specific information using a foreign namespace.
+              In the following example, a fictitious namespace <code>vendorm</code> from an "example vendor" is used
+              to provide document-level information not defined by DAPT.</p>
+            <pre class="example"
+              data-include="examples/metadata-proprietary.xml"
+              data-include-format="text">
+            </pre>
+          </div>
+          
+          <div class="advisement">
+            <strong>It is strongly recommended not to place data
+            whose semantics depend on the contents of the document
+            within <code>&lt;metadata&gt;</code> elements.</strong>
+            <p>Such data can be invalidated by <a>transformation processors</a> that
+            modify the contents of the document but preserve metadata
+            while being unaware of their semantics.
+            </p>
+          </div>
+
+          <section class="informative">
+            <h5>Defining and using foreign vocabulary that is not metadata</h5>
+            <p>If <a>foreign vocabulary</a> is included in locations other than <code>&lt;metadata&gt;</code> elements
+              it will be pruned by <a>transformation processors</a> that do not support features associated with that vocabulary,
+              as required in <a href="#unrecognised-elements-and-attributes"></a>.</p>
+            <p>A mechanism is provided to prevent such pruning, and to define semantics for such <a>foreign vocabulary</a>,
+              allowing it to be located outside a <code>&lt;metadata&gt;</code> element without being pruned,
+              and to indicate content and processor conformance:</p>
+            <ol>
+              <li>Define a profile including a feature definition for that semantic and vocabulary,
+            with a profile designator.</li>
+              <li>Signal document conformance to that profile using the <a href="#ttp-contentprofiles"></a></li>
+            </ol>
+            <p>This allows processors that support the feature to process the vocabulary
+              in whatever way is appropriate, to avoid pruning it,
+              and allows processors that do not support the feature to take
+              appropriate action, for example warning users that some functionality may be lost.</p>
+            </section>
         </section> <!-- Proprietary Metadata -->
   
       </section>
@@ -1775,7 +1927,7 @@ <h3>Namespaces</h3>
         <p>
           The following namespaces (see [[xml-names]]) are used in this specification:
         </p>
-        <table class="simple">
+        <table class="data">
           <thead>
             <tr>
               <th>Name</th>
@@ -1833,7 +1985,8 @@ <h3>Namespaces</h3>
           The namespace prefix values defined above are for convenience and <a>DAPT Documents</a> MAY use any prefix value that conforms to [[xml-names]].
         </p>
         <p>
-          The namespaces defined by this proposal document are mutable [[namespaceState]]; all undefined names in these namespaces are reserved for future standardization by the W3C.
+          The namespaces defined by this specification are mutable as described in [[namespaceState]];
+          all undefined names in these namespaces are reserved for future standardization by the W3C.
         </p>
       </section>
       <section>
@@ -1844,11 +1997,11 @@ <h3>Related Media Object (TTML)</h3>
           provides the media timeline and is the source of the <a>main programme audio</a>,
           and any visual timing references needed when adjusting timings relevant to the video image,
           such as for lip synchronization.</p>
-          <div class="example note">
-          <p>A <a>DAPT document</a> can identify the programme acting
-          as the <a>Related Media Object</a> using metadata. For example, it is possible
-          to use the <code>&lt;ebuttm:sourceMediaIdentifier&gt;</code> element defined in [[EBU-TT-3390]].</p>
-          <pre class="xml" data-include="examples/sourceMediaIdentifier.xml" data-include-format="text"></pre>
+          <div class="note">
+            <p>A <a>DAPT document</a> can identify the programme acting
+            as the <a>Related Media Object</a> using metadata. For example, it is possible
+            to use the <code>&lt;ebuttm:sourceMediaIdentifier&gt;</code> element defined in [[EBU-TT-3390]].</p>
+            <pre class="xml example" data-include="examples/sourceMediaIdentifier.xml" data-include-format="text"></pre>
           </div>
 
       </section>
@@ -1885,30 +2038,34 @@ <h3>Synchronization</h3>
       </section>
       <section>
         <h3>Profile Signaling</h3>
-        This section defines how a TTML <a>Document Instance</a> signals that it is a <a>DAPT Document</a>
+        This section defines how a TTML
+        <dfn data-cite="TTML2#terms-document-instance">Document Instance</dfn>
+        signals that it is a <a>DAPT Document</a>
         and how it signals any processing requirements that apply.
         See also <a href="#conformance-of-dapt-documents"></a>, which defines how to
         establish that a <a>DAPT Document</a> conforms to this specification.
 
         <section>
-          <h4>Profile Designator</h4>
+          <h4>Profile Designators</h4>
           <p>This profile is associated with the following profile designators:</p>
-          <table class="simple">
+          <table class="data">
             <thead>
               <tr>
                 <th>Profile Name</th>
-    
+                <th>Profile type</th>
                 <th>Profile Designator</th>
               </tr>
             </thead>
     
             <tbody>
               <tr>
-                <td><dfn data-dfn-type="dfn">DAPT 1.0 Content Profile</dfn></td>
+                <td><dfn data-dfn-type="dfn" class="export">DAPT 1.0 Content Profile</dfn></td>
+                <td><a>content profile</a></td>
                 <td><code>http://www.w3.org/ns/ttml/profile/dapt1.0/content</code></td>
               </tr>
               <tr>
-                <td><dfn data-dfn-type="dfn">DAPT 1.0 Processor Profile</dfn></td>
+                <td><dfn data-dfn-type="dfn" class="export">DAPT 1.0 Processor Profile</dfn></td>
+                <td><a>processor profile</a></td>
                 <td><code>http://www.w3.org/ns/ttml/profile/dapt1.0/processor</code></td>
               </tr>
             </tbody>
@@ -1919,11 +2076,17 @@ <h4>Profile Designator</h4>
           <h4><code>ttp:contentProfiles</code></h4>
           <p>The <dfn data-cite="TTML2#profile-attribute-contentProfiles"><code>ttp:contentProfiles</code></dfn> attribute
             is used to declare the [[TTML2]] profiles to which the document conforms.</p>
-          <p>TTML documents representing DAPT Scripts MUST specify a <a><code>ttp:contentProfiles</code></a> attribute
-            on the <code>&lt;tt&gt;</code> element including one value equal to the
-            <a>DAPT 1.0 Content Profile</a> designator.
+          <p><a>DAPT Documents</a> MUST specify a <a><code>ttp:contentProfiles</code></a> attribute
+            on the <code>&lt;tt&gt;</code> element including at least one value equal to a
+            <a>content profile</a> designator specified at <a href="#profile-designators"></a>.
             Other values MAY be present to declare conformance to other profiles of [[TTML2]],
             and MAY include profile designators in proprietary namespaces.</p>
+          <p>It is an error for a <a>DAPT Document</a> to signal conformance to a
+            <a>content profile</a> to which it does not conform.</p>
+          <p><a>Transformation processors</a> MUST NOT include values within the
+            <a><code>ttp:contentProfiles</code></a> attribute
+            associated with profiles that they (the processors) do not support;
+            by definition they cannot verify conformance of the content to those profiles.</p>
         </section>
 
         <section>
@@ -1931,7 +2094,7 @@ <h4><code>ttp:profile</code></h4>
           <p>The <dfn data-cite="TTML2#profile-attribute-profile"><code>ttp:profile</code></dfn> attribute
             is a mechanism within [[?TTML1]] for declaring the processing requirements for a <a>Document Instance</a>.
             It has effectively been superceded in [[TTML2]] by <a><code>ttp:processorProfiles</code></a>.</p>
-          <p>TTML documents representing DAPT Scripts MUST NOT specify a <code>ttp:profile</code> attribute
+          <p><a>DAPT Documents</a> MUST NOT specify a <code>ttp:profile</code> attribute
             on the <code>&lt;tt&gt;</code> element.</p>
         </section>
 
@@ -1939,10 +2102,10 @@ <h4><code>ttp:profile</code></h4>
           <h4><code>ttp:processorProfiles</code></h4>
           <p>The <dfn data-cite="TTML2#profile-attribute-processorProfiles"><code>ttp:processorProfiles</code></dfn> attribute
             is used to declare the processing requirements for a <a>Document Instance</a>.</p>
-          <p>TTML documents representing DAPT Scripts MAY specify a <a><code>ttp:processorProfiles</code></a> attribute
+          <p><a>DAPT Documents</a> MAY specify a <a><code>ttp:processorProfiles</code></a> attribute
             on the <code>&lt;tt&gt;</code> element.
-            If present, the <a><code>ttp:processorProfiles</code></a> attribute MUST include one value equal to
-            the designator of the <a>DAPT 1.0 Processor Profile</a>.
+            If present, the <a><code>ttp:processorProfiles</code></a> attribute MUST include at least one value equal to a
+            <a>processor profile</a> designator specified at <a href="#profile-designators"></a>.
             Other values MAY be present to declare additional processing constraints, 
             and MAY include profile designators in proprietary namespaces.</p>
           <p class="note">The <a><code>ttp:processorProfiles</code></a> attribute can be used
@@ -1970,7 +2133,7 @@ <h4>Other TTML2 Profile Vocabulary</h4>
             Those profile-related features are listed within <a href="#profiles"></a> as being optional. 
             They MAY be implemented in processors
             and their associated vocabulary
-            MAY be present in <a>Document Instances</a>.
+            MAY be present in <a>DAPT Documents</a>.
           </p>
           <p class="note">Unless processor support for these features and vocabulary has been
             arranged (using an out-of-band protocol), the vocabulary is not expected to be present.</p>
@@ -2128,6 +2291,220 @@ <h4>Bidirectional text</h4>
 
     </section> <!-- Profile Constraints -->
 
+    <section id="ttml-to-data-model">
+      <h2>Mapping from TTML to the DAPT Data Model</h2>
+      <p><a href="#data-model"></a> defines how objects and properties of the DAPT data model are represented in [[TTML2]], i.e. in a <a>DAPT Document</a>.
+        However, a DAPT data model instance can be represented by multiple [[TTML2]] <a>document instances</a>.</p>
+      <p>For example, <a href="#data-model"></a> does not mandate that a <code>&lt;div&gt;</code> element representing a <a>Script Event</a> be
+        a direct child of the <code>&lt;body&gt;</code> element.
+        That <code>&lt;div&gt;</code> element could be nested in another <code>&lt;div&gt;</code> element.
+        Therefore, it is possible to serialize the objects and properties of a <a>DAPT Script</a> into various <a>DAPT Documents</a>.
+        This section defines how to interoperably and unambiguously reconstruct a DAPT model instance from a <a>DAPT Document</a>.</p>
+      <p class="note">DAPT does not define a complete serialization of the DAPT data model for extensibility reasons,
+        to allow future versions to do so if needed.
+        Additionally, a <a>DAPT Document</a> can contain elements or attributes that
+        are not mentioned in the representations of DAPT objects or properties.
+        This could be because it has been generated by a processor conformant to some future version of DAPT,
+        or through a generic [[TTML2]] process,
+        or because it uses optional features, for example to add styling or layout.
+        This section defines how to process those elements or attributes.</p>
+      <p class="note">It is also possible to process <a>DAPT Documents</a> using generic [[TTML2]] processors,
+        which do not necessarily map the documents to the DAPT data model.
+        For example a generic TTML2 <a>presentation processor</a> could render an audio mix
+        based on a DAPT document without needing to model Script Events <i>per se</i>.
+        In that case, this section can be ignored.</p>
+      <section class="informative">
+        <h3>Early identification of non-conformant documents</h3>
+        <p><em>Normative provisions relating to this section are defined in [[TTML2]].</em></p>
+        <p>Since it is a requirement of DAPT that <a>DAPT Documents</a> include a
+        <code>ttp:contentProfiles</code> attribute on the root element,
+        and that the attribute includes a DAPT <a>content profile</a> designator,
+        as specified at <a href="#ttp-contentprofiles"></a>,
+        it follows that any TTML document that does not include such an attribute,
+        or does not include such a profile designator,
+        can be considered not to be a <a>DAPT Document</a>;
+        therefore a processor requiring strict adherence to DAPT could stop processing
+        such a document.</p>
+      </section>
+
+      <section>
+        <h3>Not supporting features excluded by the content profile</h3>
+        <p>A processor that takes as its input a <a>DAPT document</a> that
+          contains vocabulary relating to features that it does support,
+          but where support for those features is excluded from the content profiles
+          to which the document claims conformance, SHOULD NOT implement
+          those features in the context of that document.</p>
+      </section>
+      <section>
+        <h3>Handling <code>&lt;div&gt;</code> and <code>&lt;p&gt;</code> elements</h3>
+        <p>[[TTML2]] allows <code>&lt;div&gt;</code> elements to contain any combination of
+          <code>&lt;div&gt;</code> elements and <code>&lt;p&gt;</code> elements.
+          The DAPT data model describes how each <a>Script Event</a> is represented by
+          a <code>&lt;div&gt;</code> element that contains zero or more <code>&lt;p&gt;</code> elements.
+          It also permits other intermediate <code>&lt;div&gt;</code> elements in the path between
+          the <code>&lt;body&gt;</code> element and those <a>Script Event</a> <code>&lt;div&gt;</code> elements.
+          In addition, attributes not corresponding to properties in the DAPT data model are permitted.</p>
+        <p>This gives rise to possibilities such as:</p>
+        <ul>
+          <li><code>&lt;div&gt;</code> elements that contain children that are not <a>Text</a> objects,
+            for example other <code>&lt;div&gt;</code> elements or <code>&lt;metadata&gt;</code> elements;</li>
+          <li><code>&lt;div&gt;</code> elements that do not have attributes required for <a>Script Events</a>, like <code>xml:id</code>;</li>
+          <li><code>&lt;div&gt;</code> elements that have attributes absent from the DAPT data model for <a>Script Events</a>,
+            like <code>xml:space</code>;</li>
+          <li><code>&lt;p&gt;</code> elements whose parent <code>&lt;div&gt;</code> element does not appear to be a <a>Script Event</a>.</li>
+        </ul>
+
+        <p>The following processing rules resolve these cases.</p>
+        <p>Rules for identifying <a>Script Events</a>:</p>
+        <ol>
+          <li>A <code>&lt;div&gt;</code> element that has no <code>&lt;div&gt;</code> element children
+            and includes the TTML representations of all the mandatory properties of a <a>Script Event</a>
+            MUST be mapped to a <a>Script Event</a>,
+            such as having a valid <code>xml:id</code>
+            representing the <a>Script Event Identifier</a>,
+            even if it also contains additional <a>unrecognised vocabulary</a>;</li>
+          <li>A <code>&lt;div&gt;</code> element that contains any <code>&lt;div&gt;</code> element children
+            MUST NOT be mapped to a <a>Script Event</a>;
+            the processor instead MUST iterate through those <code>&lt;div&gt;</code> element children
+            (recursively, in a depth-first traversal) and consider if each one meets the requirements of a <a>Script Event</a>;</li>
+          <li>Any remaining unmapped <code>&lt;div&gt;</code> elements MUST NOT be mapped to a <a>Script Event</a>.</li>
+        </ol>
+        
+        <p>Rules for identifying <a>Text</a> objects:</p>
+        <ol>
+          <li>A <code>&lt;p&gt;</code> element that is a child of a <code>&lt;div&gt;</code> element
+            that maps to a <a>Script Event</a> MUST be mapped to a <a>Text</a> object.</li>
+          <li>A <code>&lt;p&gt;</code> element that is not a child of a <code>&lt;div&gt;</code> element
+            that maps to a <a>Script Event</a> MUST NOT be mapped to a <a>Text</a> object.</li>
+        </ol>
+
+        <p class="note">Future versions of DAPT could include features that use these
+          structural possibilities differently,
+          and therefore define other processing rules that are mutually exclusive
+          with the rules defined here.
+        </p>
+
+        <aside class="example">This example demonstrates the above possibilities,
+          and the application of the rules:
+          <pre
+            data-include="examples/non-dapt-divs.xml"
+            data-include-format="text">
+          </pre>
+
+          <p>The result of applying the above rules to this example is:</p>
+          <ul>
+            <li><code>d1</code> is a <a>Script Event</a> and its child <code>&lt;p&gt;</code> element is a <a>Text</a> object;</li>
+            <li>The <code>&lt;div&gt;</code> element between <code>d1</code> and
+              <code>d2</code>'s parent <code>&lt;div&gt;</code> element is not a <a>Script Event</a>
+              and its child <code>&lt;p&gt;</code> element is not a <a>Text</a> object;</li>
+            <li><code>d2</code> is a <a>Script Event</a> and its parent <code>&lt;div&gt;</code> element is not;</li>
+            <li><code>d3</code> is a <a>Script Event</a> and its parent and its grandparent <code>&lt;div&gt;</code> elements are not;</li>
+            <li><code>d4_1</code> is not a <a>Script Event</a> and its child <code>&lt;p&gt;</code> element is not a <a>Text</a> object;</li>
+            <li><code>d4_2</code> is a <a>Script Event</a>.</li>
+          </ul>
+        </aside>
+      </section>
+
+      <section class="informative">
+        <h3>Using computed attribute values</h3>
+        <p><em>Some normative provisions relating to this section are defined in [[TTML2]].</em></p>
+        <p>Some attributes have semantics for computing their value that depend on the computed value of
+          the attribute on some other element.
+          For example if the <code>xml:lang</code> attribute is not specified on an element then its computed
+          value is the computed value of the same attribute on the element's parent.</p>
+        <p>Or, for another example, the computed times of an element in a DAPT document are relative
+          to the begin time of its parent element. If a <code>&lt;div&gt;</code> element specifies a <code>begin</code>
+          attribute, and that element does not correspond to a <a>Script Event</a>, then the computed times
+          of its descendant <code>&lt;div&gt;</code> elements that do correspond to <a>Script Events</a>
+          are different to what they would be if that intermediate <code>&lt;div&gt;</code> element's <code>begin</code>
+          time were ignored.</p>
+        <p class="ednote">MAYBE REMOVE Or, also for example, if styling is used in a TTML document, the computed value of the <code>tts:fontSize</code>
+          attribute when expressed as a percentage is relative to the computed value of the same attribute
+          on the element's parent.
+          Furthermore, in this example, the algorithm for generating ISDs (Intermediate Synchronic Documents)
+          involves reparenting some elements. The computed value that applies is the one <em>before</em>
+          rehoming has taken place.</p>
+        <p>Considering this situation more generally,
+          it is possible that, within a DAPT document, there can be TTML elements that
+          do not directly correspond to objects in the DAPT data model,
+          and those elements can specify attributes
+          that affect the computation of attribute values that apply to elements that do correspond to
+          objects in the DAPT data model.</p>
+        <p>The semantics defined by [[TTML2]] or, for vocabulary defined herein, this specification, take precedence in this scenario.
+          Implementations MUST compute attribute values based on the contents of the <a>document instance</a> <em>before</em>
+          applying those computed values to DAPT data model objects.
+        </p>
+        <aside class="example">
+          <p>This example demonstrates these possibilities,
+            which a processor might need to handle:</p>
+          <pre
+            data-include="examples/non-dapt-div-with-begin-and-lang.xml"
+            data-include-format="text">
+          </pre>
+          <p>Here, the <code>&lt;div&gt;</code> elements that correspond to <a>Script Events</a>,
+            which have ids <code>d1</code> and <code>d2</code>,
+            are otherwise (apart from their identifiers) identical,
+            yet their language and <a>Begin</a> properties have different computed values,
+            due to the attributes specified on the <code>&lt;div&gt;</code> element parent of <code>d2</code>.</p>
+        </aside>
+        <!-- deliberate duplication of the statement before the example follows, for emphasis: -->
+        <p>If an implementation internally creates DAPT data model objects,
+          such as the <a>Script Events</a> shown in the example above,
+          it is important for interoperability that they use the computed values.</p>
+      </section>
+
+      <section class="informative">
+        <h3>Considerations for transformation and validation processors</h3>
+
+        <section>
+          <h3>Retaining unrecognised vocabulary</h3>
+          <p>As per <a href="#unrecognised-elements-and-attributes"></a>,
+            implementers of DAPT processors are encouraged to maintain <a>unrecognised vocabulary</a>
+            within <code>&lt;metadata&gt;</code> elements in <a>DAPT Documents</a>.
+            In practice it is possible that an implementation which both inputs DAPT documents
+            and outputs DAPT documents might modify the input
+            document structure and contents, and while doing so,
+            effectively prune those entities with <a>unrecognised vocabulary</a> from the output document.</p>
+        </section>
+
+        <section>
+          <h3>Validation warnings and errors</h3>
+          <p><em>Normative provisions relating to this section are defined in [[TTML2]].</em></p>
+          <p>[[TTML2]] defines a <dfn data-cite="TTML2#terms-validation-processor">validation processor</dfn>,
+            a class of implementation whose purpose is
+            to assess a <a>document instance</a> and decide if it is valid or not.
+            Typically this would be used within a processing workflow
+            to check that documents are acceptable for onward usage.
+            A real world example would likely not return simply "good" or "bad",
+            but also output informational, warning and error messages
+            describing unusual, unexpected or problematic contents in the input document.
+          </p>
+          <p>When implementing a <a>validation processor</a> for a <a>DAPT document</a>,
+            strict [[TTML2]] validation processing rules can be applied.
+            Doing this involves checking for the presence and semantic validity of
+            syntax and content associated with required or optional features defined in the
+            profile, and checking for the absence of syntax associated with prohibited features.
+          </p>
+          <p>The [[TTML2]] mechanism for dealing with vocabulary in unrecognised namespaces is
+            to prune it prior to validation.
+            This approach can be used; additionally it could be reasonable for
+            an implementation to report as information those attributes and elements
+            that have been pruned.
+          </p>
+          <p class="note">The term "vocabulary" here refers to XML elements and attributes.</p>
+          <p>Validation warnings could be issued when unsupported or deprecated
+            vocabulary in recognised namespaces is encountered after pruning,
+            or when supported vocabulary contains unexpected but not invalid content,
+            but in these scenarios errors are not expected.
+          </p>
+          <p>Validation errors are expected when prohibited vocabulary is present,
+            or when semantically invalid content within permitted vocabulary
+            is encountered.
+          </p>
+        </section>
+      </section>
+  </section> <!-- #ttml-to-data-model -->
+
   <section id="conformance"><!-- keep section id, not use h2 -->
     <p>[[TTML2]] specifies a formal language for expressing document and processor requirements,
       within the <a href="https://www.w3.org/TR/ttml2/#vocabulary-profiling">Profiling</a> sub-system.
@@ -2145,15 +2522,22 @@ <h4>Bidirectional text</h4>
       profile processing semantics can use the TTML2 profiles defined in <a href="#profiles"></a>
       directly to determine if it is capable of processing a <a>DAPT document</a>.
     </p>
+
     <section>
       <h3>Conformance of <a>DAPT Documents</a></h3>
-      <p>Conformant <a>DAPT Documents</a> are [[TTML2]] <a>Document Instances</a> that
+      <p>Conformant <a>DAPT Documents</a> are [[TTML2]] <a>timed text content document instances</a> that
         conform to the normative provisions of this specification.
         Those provisions are expressed using the 
         <a href="https://www.w3.org/TR/ttml2/#profile">profile</a> vocabulary of [[TTML2]] in the
         <dfn data-cite="ttml2#terms-content-profile">content profile</dfn> defined
         in <a href="#profiles"></a>.</p>
+      <p class="note">
+        <a>DAPT Documents</a> remain subject to the content conformance requirements specified at Section 3.1 of [[TTML2]].
+        In particular, a <a>DAPT Document</a> can contain <a>foreign vocabulary</a>,
+        since such elements and attributes are pruned by the algorithm at Section 4 of [[TTML2]] prior to evaluating content conformance.
+      </p>
     </section> <!-- content-profile-conformance-section -->
+
     <section>
       <h3>Conformance of DAPT Processors</h3>
       <p>Conformant DAPT Processors are [[TTML2]]
@@ -2282,7 +2666,7 @@ <h3>Profiles</h3>
       and any extensions or constraints.
     </p>
     <p>
-      A <dfn data-cite="TTML2#terms-document-instance">Document Instance</dfn>
+      A <dfn data-cite="TTML2#terms-timed-text-content-document-instance">timed text content document instance</dfn>
       that conforms to the <a>content profile</a> defined herein:
     </p>
     <ul style="list-style-type:disc">
@@ -2292,8 +2676,8 @@ <h3>Profiles</h3>
       <li>MUST NOT include any vocabulary, syntax or attribute value associated with a <a>feature</a> or <a>extension</a> whose disposition is prohibited in the profile.</li>
     </ul>
     <p class="note">
-      A <a>Document Instance</a>, by definition, satisfies the requirements of Section 3.1 at [[TTML2]],
-      and hence a <a>Document Instance</a> that conforms to a profile defined herein is also a conforming TTML2 <a>Document Instance</a>.
+      A <a>timed text content document instance</a>, by definition, satisfies the requirements of Section 3.1 at [[TTML2]],
+      and hence a <a>timed text content document instance</a> that conforms to a profile defined herein is also a conforming TTML2 <a>Document Instance</a>.
     </p>
     <p>
       A <dfn data-cite="TTML2#terms-presentation-processor">Presentation processor</dfn> that conforms to the <a>processor profile</a> defined in this specification:
@@ -2368,7 +2752,7 @@ <h3>Profiles</h3>
     </p>
     <p class="note">
       This document does not specify <a>presentation processor</a> or <a>transformation processor</a> behavior
-      when processing or transforming a non-conformant <a>Document Instance</a>.
+      when processing or transforming a non-conformant <a>timed text content document instance</a>.
     </p>
     <p class="note">
       The permitted and prohibited dispositions do not refer to the specification of
@@ -2392,7 +2776,7 @@ <h4>Disposition of Features and Extensions</h4>
       </p>
       <p class="ednote">Editorial task: go through this list of <a>features</a> and check the disposition of each.
         There should be no prohibited features that are permitted in IMSC.</p>
-      <table class="simple" id="table-features-and-extensions">
+      <table class="data" id="table-features-and-extensions">
         <thead>
           <tr>
             <th style="width:20%; text-align:center;">Feature or Extension</th>
@@ -2812,6 +3196,13 @@ <h4>Disposition of Features and Extensions</h4>
               This is the profile expression of <a href="#represents"></a>.
             </td>
           </tr>
+          <tr>
+            <td><a href="#scripteventmapping"><code>#scriptEventMapping</code></a></td>
+            <td><span class="optional label">optional</span></td>
+            <td>
+              This is the profile expression of <a href="#handling-div-and-p-elements"></a>.
+            </td>
+          </tr>
           <tr>
             <td><a href="#scripttype-root"><code>#scriptType-root</code></a></td>
             <td><span class="required label">required</span></td>
@@ -2877,7 +3268,7 @@ <h4>DAPT Content Profile</h4>
           using the profile mechanism of [[TTML2]].
           It can be used by a validating processor that supports the DAPT Processor Profile
           to validate a <a>DAPT Document</a>.</p>
-        <p>There is no requirement to include the DAPT Content Profile within a <a>Document Instance</a>.</p>
+        <p>There is no requirement to include the DAPT Content Profile within a <a>DAPT Document</a>.</p>
         <pre class="xml" data-include="profiles/dapt-content-profile.xml" data-include-format="text"></pre>
       </section>
 
@@ -2887,7 +3278,7 @@ <h4>DAPT Processor Profile</h4>
           using the profile mechanism of [[TTML2]].
           A processor that supports the required features and extensions of the DAPT Processor Profile
           can, minimally, process all permitted features within a <a>DAPT Document</a>.</p>
-        <p>There is no requirement to include the DAPT Processor Profile within a <a>Document Instance</a>.</p>
+        <p>There is no requirement to include the DAPT Processor Profile within a <a>DAPT Document</a>.</p>
         <pre class="xml" data-include="profiles/dapt-processor-profile.xml" data-include-format="text"></pre>
     </section>
 
@@ -2981,11 +3372,23 @@ <h3>#represents-root</h3>
 
         <p>An example of a <a>transformation processor</a> that supports this extension is
           a validating processor that reports an error if the extension is required by a
-          <a>content profile</a> but the <a>Document Instance</a> claiming
+          <a>content profile</a> but the <a>timed text content document instance</a> claiming
           conformance to that profile either does not have a
           <a><code>daptm:represents</code></a> attribute on the <code>&lt;tt&gt;</code> element
           or has one whose value is not conformant with the requirements defined herein.</p>
+      </section>
 
+      <section>
+        <h3>#scriptEventMapping</h3>
+        <p>A <a>transformation processor</a> supports the <code>#scriptEventMapping</code> extension
+          if, when mapping a <a>DAPT document</a> into an internal representation of the DAPT data model,
+          it implements the processing requirements specified at <a href="#handling-div-and-p-elements"></a>.</p>
+
+        <p class="note">No support for the <code>#scriptEventMapping</code> extension is
+          required for <a>presentation processors</a> because there are no presentation semantics that
+          either require, or depend upon, mapping a <a>DAPT document</a> into an internal representation
+          of the DAPT data model. A presentation processor that does perform such a mapping can also be
+          considered to be a <a>transformation processor</a> for the purpose of this extension.</p>
       </section>
 
       <section>
@@ -3003,7 +3406,7 @@ <h3>#scriptType-root</h3>
           when the SHOULD requirements defined in <a href="#script-type"></a> for a
           <a>DAPT Document</a>'s <a><code>daptm:scriptType</code></a> are not met,
           and that reports an error if the extension is required by a
-          <a>content profile</a> but the <a>Document Instance</a> claiming
+          <a>content profile</a> but the <a>timed text content document instance</a> claiming
           conformance to that profile either does not have a
           <a><code>daptm:scriptType</code></a> attribute on the <code>&lt;tt&gt;</code> element
           or has one whose value is not defined herein.</p>
diff --git a/profiles/dapt-content-profile.xml b/profiles/dapt-content-profile.xml
index 50651b7..4c9ff64 100644
--- a/profiles/dapt-content-profile.xml
+++ b/profiles/dapt-content-profile.xml
@@ -91,6 +91,7 @@
     <!-- optional (voluntary) extension support -->
     <extension value="optional">#agent</extension>
     <extension value="optional">#onScreen</extension>
+    <extension value="optional">#scriptEventMapping</extension>
     <extension value="optional">#textLanguageSource</extension>
     <!-- prohibited extension support -->
     <extension value="prohibited">#profile-root</extension>
diff --git a/profiles/dapt-processor-profile.xml b/profiles/dapt-processor-profile.xml
index e613a3c..4fd8f9c 100644
--- a/profiles/dapt-processor-profile.xml
+++ b/profiles/dapt-processor-profile.xml
@@ -93,6 +93,7 @@
     <extension value="required">#xmlLang-root</extension>
     <!-- optional (voluntary) extension support -->
     <extension value="optional">#profile-root</extension>
+    <extension value="optional">#scriptEventMapping</extension>
     <extension value="optional">#source-data</extension>
     <extension value="optional">#xmlLang-audio-nonMatching</extension>
 </extensions>