Redraft opening section of §2.1 (#183)

Thanks for all the review inputs, merging.

* Redraft opening section of §2.1

Closes #175.

* Tweak language

Remove "English", and clarify that we are using domain-specific terms in place of the general usage.

* Attempt to address feedback

Clarify that a transcript is a type of script in general usage.

* Remove standalone use of "script"

Always clarify whether we mean transcript, or script, or both. Changes only required in the Introduction to achieve this.

index.html

@@ -159,14 +159,22 @@ <h2>Scope</h2>
       <h2>Introduction</h2>
       <section>
         <h3>Transcripts and Scripts</h3>
-        <p>A <dfn>transcript</dfn> is a text representation of <i>pre-existing</i> media in another form,
-          for example the dialogue in a video.
-          A <dfn>script</dfn> is a text representation of the <i>intended</i> content of media prior to its creation,
-          for example to guide an actor in recording an audio track.
-          Within this specification the term <a>DAPT script</a> is used generically to refer to both <a>transcripts</a> and <a>scripts</a>.
+        <p>In general usage, one meaning of the word <em>script</em> is
+          the written text of a film, television programme, play etc.
+          A script can be either a record of the completed production,
+          also known as a transcript,
+          or as a plan for a yet to be created production.
+          In this document, we use domain-specific terms, and define more specifically that:</p>
+        <ul>
+          <li>a <dfn>transcript</dfn> is the text representation of <em>pre-existing</em> media in another form,
+            for example the dialogue in a video;</li>
+          <li>a <dfn>script</dfn> is a text representation of the <em>intended</em> content of media prior to its creation,
+        for example to guide an actor in recording an audio track.</li>
+        </ul>
+        <p>The term <a>DAPT script</a> is used generically to refer to both <a>transcripts</a> and <a>scripts</a>,
+          and is a point of conformance to the formal requirements of this specification.
           <a>DAPT Scripts</a> consist of timed text and associated metadata,
-          such as the character speaking.
-        </p>
+          such as the character speaking.</p>
         <p>In dubbing workflows, a <a>transcript</a> is generated and translated to create a <a>script</a>.
           In audio description workflows, a <a>transcript</a> describes the video image,
           and is then used directly as a <a>script</a> for recording an audio equivalent.
@@ -264,17 +272,17 @@ <h4>Basic document structure</h4>
           <li>The <code>&lt;tt&gt;</code> root element in the namespace <code>http://www.w3.org/ns/ttml</code> indicates that this is a TTML document
           and the <a><code>ttp:contentProfiles</code></a> attribute indicates that it adheres to the DAPT <a>content profile</a> defined in this specification.</li>
           <li>The <code>daptm:workflowType</code> attribute indicates the type of workflow.</li>
-          <li>The <code>daptm:scriptType</code> attribute indicates the type of script
-          but in this empty example, it is not relevant, as only the structure of the document is shown.</li>
+          <li>The <code>daptm:scriptType</code> attribute indicates the type of <a>transcript</a> or <a>script</a>
+          but in this empty example, it is not relevant, since only the structure of the document is shown.</li>
         </ul>
         <p>The structure is applicable to all types of <a>DAPT scripts</a>, dubbing or <a>audio description</a>.</p>
         <pre class="example"
           data-include="examples/intro-top-level.xml"
           data-include-format="text">
         </pre>
-        <p>The following examples correspond to the timed text <a>scripts</a> produced
+        <p>The following examples correspond to the timed text <a>transcripts</a> and <a>scripts</a> produced
           at each stage of the workflow described in [[DAPT-REQS]].</p>
-        <p>The first example shows a <a>script</a> where timed opportunities for descriptions
+        <p>The first example shows an early stage <a>transcript</a> in which timed opportunities for descriptions
           or transcriptions have been identified but no text has been written:</p>
         <pre class="example"
           data-include="examples/intro-times-only.xml"
@@ -321,7 +329,7 @@ <h4>Audio Description Examples</h4>
           data-include-format="text">
         </pre>
         <p>It is also possible to embed the audio directly,
-          so that a single document contains all of the script and
+          so that a single document contains the <a>script</a> and
           recorded audio together:
         </p>
         <pre class="example"
@@ -330,7 +338,7 @@ <h4>Audio Description Examples</h4>
         </pre>
 
         <h4>Dubbing Examples</h4>
-        <p>From the basic structure of Example 1, a transcription of the audio programme produces an original language dubbing <a>script</a>,
+        <p>From the basic structure of <a href="#example-1"></a>, a transcription of the audio programme produces an original language dubbing <a>script</a>,
           which can look as follows. No specific style or layout is defined, and here the focus is on the transcription of the dialogs.
           Characters are identified within the <code>&lt;metadata&gt;</code>.</p>
         <pre class="example"