replacing an attribute at WSDL file from a Deployment plan XML

Question

I have two files WSDL file and Deployment plan file. I am trying to replace an attribute at the WSDL file from the Deployment plan file.

WSDL file

<wsdl:definitions
   name="Project"
   targetNameSpace="http://xxx/yyy/project"
   xmlns:ns0="http://xxx/zzz"&gt;

   <wsdl:types>
       <xs:schema>
        .....
       </sx:schema>
   </wsdl:types>
</wsdl:definitions>

deployment plan file

<deployment-plan>
  <application-name>Project</application-name>
  <variable-definition>
    <variable>
       <name>ErrCode</name>
       <value>2</value>
    </variable>
  </variable-definition>
  <module-override>
    <module-descriptor external="false">
      <root-element>wsdl:definitions</root-element>
      <uri>WEB-INF/wsdl/project.wsdl</uri>
      <variable-assignment>
        <name>ErrCode</name>
        <xpath>/wsdl:definitions/@xmlns:ns0</xpath>
        <operation>replace</operation>
      </variable-assignment>
    </module-descriptor>
  </module-override>
</deployment-plan>

When I deploy both of them to the server the value of xmlns:ns0 doesn't change.