title: XML Schema 1.1 not recognizing 'assert' or 'assertion'
body: <p>I am trying to use the following in an <em>XSD</em></p>
  
  <pre><code>&lt;xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" &gt;
  &lt;xs:element name="dimension"&gt;
    &lt;xs:complexType&gt;
      &lt;xs:attribute name="height" type="xs:int"/&gt;
      &lt;xs:attribute name="width" type="xs:int"/&gt;
      &lt;xs:assert test="@height = @width"/&gt;
    &lt;/xs:complexType&gt;
  &lt;/xs:element&gt;
  </code></pre>
  
  <p>I know assert/assertion are part of XML Schema 1.1 but not 1.0. However everything I have read indicates the <em>namespace</em> is the same for both: <a href="http://www.w3.org/2001/XMLSchema">http://www.w3.org/2001/XMLSchema</a></p>
  
  <p>A minor problem is that the program I am using to write the Schema (Microsoft Visual Studio) does not recognize the 'assert' element, saying the 'the element <em>complexType</em> in namespace (...) has invalid child element 'assert'. </p>
  
  <p>The main problem is that when I actually try to validate an XML against this schema, using xmllint, it throws up an error saying </p>
  
  <pre><code>" element assert: Schemas parser error : Element '{http://www.w3.org/2001/XMLSchema}complexType': The content is not valid. Expected is (annotation?, (simpleContent | complexContent | ((group | all | choice | sequence)?, ((attribute | attributeGroup)*, anyAttribute?))))
  </code></pre>
  
  <p>Is 1.1 simply not recognized by xmllint/visual studio, despite being pointed to the 1.1 namespaces?</p>