Explain the two different XML structures for adding and modifying strings.

Signed-off-by: Stefan Eike
Signed-off-by: Stefan Eike <stefan.eike@mailbox.org>

Author: Stefan Eike

topics/plugin-addgeneratedtext.dita

@@ -44,6 +44,22 @@
           <dd>Add new strings to generated text file. </dd>
         </dlentry>
       </dl>
+      <note id="note_gff_13d_fqb">There are two different XML structures for adding new or modifying
+        existing strings. Both can be used with the latest DITA-OT. The new structure (root element
+          <xmlelement>vars</xmlelement>) has the benefit to add custom parameters to the string,
+        such as the current page number, but the old structure (root element
+          <xmlelement>strings</xmlelement>) is still valid. For example, the old structure is still
+        used in the <b>org.dita.base</b> plugin and the new structure is used in
+          <b>org.dita.pdf2</b>. The following code snippets represent the same information in the
+        old and the new structure. If you are interested in the capabilities of the parameter
+        mechanism, please have a look at the XML files stored in
+          <filepath>org.dita.pdf2\cfg\common\vars</filepath>.<codeblock id="codeblock_hnb_h3d_fqb" outputclass="language-xml normalize-space show-line-numbers show-whitespace">&lt;?xml version="1.0" encoding="utf-8"?>
+&lt;strings xml:lang="en-US">
+  &lt;str name="String1">English generated text&lt;/str>
+&lt;/strings></codeblock><codeblock id="codeblock_lxd_k3d_fqb" outputclass="language-xml normalize-space show-line-numbers show-whitespace">&lt;?xml version="1.0" encoding="UTF-8"?>
+&lt;vars xmlns="http://www.idiominc.com/opentopic/vars">
+  &lt;variable id="String1">English generated text&lt;/variable>
+&lt;/vars></codeblock></note>
     </section>
     <example>
       <title>Example: adding new strings</title>