title: XSD annotation and documentation elements, and how to use them
body: <p>We are creating xml files that we want to be compliant with the following xsd: <a href="http://www.topografix.com/gpx/1/1/gpx.xsd" rel="nofollow">http://www.topografix.com/gpx/1/1/gpx.xsd</a>  This xsd supports '...extending by adding your own elements here ...', see the extensionsType, which I have copied below for convenience.</p>
  
  <p>1) I don't understand whether annotation and documentation are literal element names that would appear in compliant xml.  I believe they are not but need confirmation.  I'm assuming then that a compliant document would simply have any number of our own custom elements anywhere inside of any [extensions] element, correct?</p>
  
  <p>2) Why are there <strong>two</strong> pairs of annotation/documentation elements below, with one in a sequence?</p>
  
  <pre><code> &lt;xsd:complexType name="extensionsType"&gt;
         &lt;xsd:annotation&gt;
          &lt;xsd:documentation&gt;
           You can add extend GPX by adding your own elements from another schema here.
          &lt;/xsd:documentation&gt;
         &lt;/xsd:annotation&gt;
          &lt;xsd:sequence&gt;
           &lt;xsd:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"&gt;
             &lt;xsd:annotation&gt;
              &lt;xsd:documentation&gt;
               You can add extend GPX by adding your own elements from another schema here.
              &lt;/xsd:documentation&gt;
             &lt;/xsd:annotation&gt;
           &lt;/xsd:any&gt;
          &lt;/xsd:sequence&gt;
        &lt;/xsd:complexType&gt;
  </code></pre>