SOAP Faults in XKMS

Hi,

Section 3.4 in Part-II of XKMS specification defines the use of SOAP Faults in XKMS. There is following example provided to explain the use of SOAP Fault in XKMS.
<?xml version="1.0" ?>
<env:Envelope xmlns:env="http://www.w3.org/2002/06/soap-envelope">
 <env:Body>
  <env:Fault>
    <env:Code>
      <env:Value>env:Sender</env:Value>
      <env:Subcode>
        <env:Value>xkms:MessageNotSupported</env:Value>
      </env:Subcode>
    </env:Code>
    <env:Reason>LocateRequest message not supported</env:Reason>
   </env:Fault>
 </env:Body>
</env:Envelope>

I am confused with use of  prefix "env" and "xkms" in values of some Text Nodes e.g. "env:Sender" and "xkms:MessageNotSupported". Can anybody explain why this convention is being followed? Can we use the Text Nodes without these prefixes? If the use of these prefixes is necessary and these prefixes relates the Text Nodes to the corresponding namespaces then the above mentioned example don't define the XML namespace for "xkms". Any details on this issue would be highly appreciated.

Thanx & Regards,

Yasir Khan