title: XSD syntax for XML attributes with namespace
body: <p>I have an xml fragment for which I need to write XSD</p>
  
  <pre><code>&lt;root xmlns="http://xmlns.oracle.com/sca/1.0" xmlns:id="http://xmlns.oracle.com/id/1.0"&gt;
    &lt;service name="Book" id:number="465"/&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p>The following XSD gives error while JAXB class generation.</p>
  
  <pre><code>&lt;xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://xmlns.oracle.com/sca/1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
    &lt;xs:element name="root"&gt;
      &lt;xs:complexType&gt;
        &lt;xs:sequence&gt;
          &lt;xs:element name="service"&gt;
            &lt;xs:complexType&gt;
              &lt;xs:simpleContent&gt;
                &lt;xs:extension base="xs:string"&gt;
                  &lt;xs:attribute type="xs:string" name="name"/&gt;
                  &lt;xs:attribute ref="ns:number" xmlns:ns="http://xmlns.oracle.com/id/1.0"/&gt;
                &lt;/xs:extension&gt;
              &lt;/xs:simpleContent&gt;
            &lt;/xs:complexType&gt;
          &lt;/xs:element&gt;
        &lt;/xs:sequence&gt;
      &lt;/xs:complexType&gt;
    &lt;/xs:element&gt;
    &lt;/xs:schema&gt;
  </code></pre>
  
  <p>Error is</p>
  
  <p>C:\Program Files\Java\jdk1.7.0_06\bin>xjc -p test C:\book.xsd
  parsing a schema...
  [ERROR] src-resolve.4.2: Error resolving component 'ns:number'. It was detected
  that 'ns:number' is in namespace 'http://xmlns.oracle.com/id/1.0', but component
  s from this namespace are not referenceable from schema document 'file:/C:/book.
  xsd'. If this is the incorrect namespace, perhaps the prefix of 'ns:number' need
  s to be changed. If this is the correct namespace, then an appropriate 'import'
  tag should be added to 'file:/C:/book.xsd'.
    line 10 of file:/C:/book.xsd</p>