title: Error: Undeclared namespace prefix x:
body: <p>I am a SOAP newbie and struggling with how to resolve this error message,</p>
  
  <blockquote>
    <p>{:error, "500",      "Undeclared namespace prefix \"x\"\n at [row,col
    {unknown-source}]: [1,168]"}</p>
  </blockquote>
  
  <p>for the below SOAP envelope.  Because of terms and conditions of the host system I am trying to access, I have replaced identifying URL and credential info with "xxx" and removed the majority of objects.</p>
  
  <pre><code>&lt;x:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
              xmlns:read="urn://xxx/sdk/ReadObject" 
              xmlns:obj="http://xxx/object"&gt;
      &lt;x:Header&gt;
          &lt;wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"
                         xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"&gt;
              &lt;wsse:UsernameToken&gt;
                  &lt;wsse:Username&gt;xxx&lt;/wsse:Username&gt;
                  &lt;wsse:Password Type="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-username-token-profile-1.0#PasswordText"&gt;xxx&lt;/wsse:Password&gt;
              &lt;/wsse:UsernameToken&gt;
          &lt;/wsse:Security&gt;
      &lt;/x:Header&gt;
      &lt;x:Body&gt;
        &lt;read:readEstimate&gt;
          &lt;read:estimate&gt;
          &lt;obj:id&gt;38945&lt;/obj:id&gt;
          &lt;/read:estimate&gt;
        &lt;/read:readEstimate&gt;
      &lt;/x:Body&gt;
  &lt;/x:Envelope&gt;
  </code></pre>