title: XSD nested sequence tags. Is this valid XSD?
body: <p>Is this XSD fragment valid? </p>
  
  <pre><code>  &lt;xs:complexType name="ShippingPointStructure"&gt;
      &lt;xs:sequence&gt;
        &lt;xs:element minOccurs="0" maxOccurs="unbounded" ref="DeliveryID" /&gt;
        &lt;xs:element minOccurs="0" ref="DeliveryDate" /&gt;
        &lt;xs:sequence minOccurs="0" maxOccurs="unbounded"&gt;
          &lt;xs:element minOccurs="0" ref="WarehouseID" /&gt;
          &lt;xs:element minOccurs="0" ref="LocationID" /&gt;
        &lt;/xs:sequence&gt;
        &lt;xs:element minOccurs="0" ref="Address" /&gt;
      &lt;/xs:sequence&gt;
    &lt;/xs:complexType&gt;
  </code></pre>
  
  <p>I have never seen a sequence node as a direct child of another sequence node. I've googled for awhile but can't find an answer. The XSD file has been run through some online validators with success - but I suspect they are only checking for XML validity.</p>
  
  <p>Can anyone suggest what the XML may need to look like? Something like this perhaps:</p>
  
  <pre><code>&lt;ShippingPointStructure&gt;
      &lt;DeliveryID&gt;&lt;/DeliveryID&gt;
      &lt;DeliveryDate&gt;&lt;/DeliveryDate&gt;
  
      &lt;WarehouseID&gt;&lt;/WarehouseID&gt;
      &lt;LocationID&gt;&lt;/LocationID&gt;
      &lt;WarehouseID&gt;&lt;/WarehouseID&gt;
      &lt;LocationID&gt;&lt;/LocationID&gt;
      &lt;WarehouseID&gt;&lt;/WarehouseID&gt;
      &lt;LocationID&gt;&lt;/LocationID&gt;
  
      &lt;Address&gt;&lt;/Address&gt;
  &lt;/ShippingPointStructure&gt;
  </code></pre>
  
  <p>Any help appreciated.</p>
  
  <p>Background:</p>
  
  <p>This is fragment of an official XSD file provided by a European government department. I cannot contact the creator as it comes through several layers of clients. </p>