how to rectify the xml error "command not find declaration of element"?

Question

I have the code below, its giving me the error near right angular bracket of scenario('>'). The error is "Can not find declaration of element 'scenario'. Some XML validators are saying that this document contains no errors and the others are throwing the above error. This is the authorisation file for diameter protocol testing. Does anybody knows the cause and how to resolve it??

<?xml version="1.0" encoding="ISO-8859-1" ?>
    <scenario>
    <init>
      <send channel="trans-ip-v5">
        <command name="CER">
          <avp name="Origin-Host" value="pruthvi.localhost.com"> </avp>
          <avp name="Origin-Realm" value="pruthvi.com"> </avp>
          <avp name="Auth-Application-Id" value="4"> </avp>
         </command>

      </send>
        <receive channel="trans-ip-v5">
        <command name="CEA">
        </command>
      </receive>
    </init>

    <!-- Traffic -->
    <traffic>
    <send channel="trans-ip-v5">


    <command name="AAAR">
    <avp name="Session-Id" value="sha12345"> </avp>
    <avp name="CC-Request-Type" value="1"> </avp>
    <avp name="CC-Request-Number" value="1"> </avp>
    <avp name="User-Name" value="[email protected]"> </avp>
    <avp name="Auth-Application-Id" value="4"> </avp>
    <avp name="Origin-Host" value="pruthvi.localhost.com"> </avp>
    <avp name="Origin-Realm" value="pruthvi.com"> </avp>
    <avp name="Destination-Realm" value="BRM"> </avp>
    <avp name="Destination-Host" value="bgl-07"> </avp>

    <avp name="Subscription-Id">
       <avp name="Subscription-Id-Type" value="0"> </avp> 
       <avp name="Subscription-Id-Data" value="pruthvi_test"> </avp>
    </avp>


    <avp name="Multiple-Services-Indicator" value="1"> </avp>


    <avp name="Multiple-Services-Credit-Control"> 

    <!--
    <avp name="Requested-Service-Unit">
       <avp name="CC-Time" value="1000"> </avp>
    </avp>
    -->

    <!--
    <avp name="Used-Service-Unit">
     <avp name="CC-Time" value="890"> </avp>  
    </avp>
    -->


    <avp name="Requested-Service-Unit">
       <avp name="CC-Total-Octets" value="524288"> </avp>
    </avp>



    <avp name="Used-Service-Unit">
       <avp name="CC-Output-Octets" value="262144"> </avp>
      <avp name="CC-Input-Octets" value="262144"> </avp> 
    </avp>


    <!--
    <avp name="Service-Identifier" value="222"> </avp>
    -->
    </avp>

    <avp name="Nas-Port" value="570433720"> </avp>
    <avp name="Nas-Port-Type" value="0"> </avp>
    <avp name="Nas-Ip-Address" value="10.223.100.1"> </avp>
    <avp name="Nas-Identifier" value="adl-ras-bng-vck-01"> </avp>
    <avp name="Framed-Ip-Address" value="117.199.228.2"> </avp>
    <avp name="Calling-Station-Id" value="94:5f:z9:02:z5:d0"> </avp>
    <avp name="Service-Context-Id" value="www.pruthvi.com"> </avp>


    </command>
    </send>
    <receive channel="trans-ip-v5">

    <command name="AAAA">
    </command>
    </receive>
    <!--
    <wait-ms value="5000"></wait-ms>
    -->
    </traffic>

    </scenario>