title: How to fix an XSD validation error?
body: <p>I have an XML form with an element 0, which is well-formed but not valid. 
  When I try to validate it XMLSpy I get a following error: 
  Nothing is allowed inside empty element 'hidden'.
  Below is my schema:</p>
  
  <pre><code>&lt;xs:element name="hidden"&gt;
      &lt;xs:complexType&gt;
          &lt;xs:attribute name="datatype" type="xs:string" use="optional"/&gt;
          &lt;xs:attribute name="alias" type="xs:string" use="optional"/&gt;
          &lt;xs:attribute name="source" type="xs:string" use="optional"/&gt;
          &lt;xs:attribute name="name" type="xs:string" use="required"/&gt;
          &lt;xs:attribute name="lookup" type="xs:string" use="optional"/&gt;
      &lt;/xs:complexType&gt;
  &lt;/xs:element&gt;
  </code></pre>
  
  <p>What do I need to add to the above schema to fix this error? Thanx ml</p>