Hello all. I have a problem

I have a document :

<otx xmlns="http://iso.org/OTX/1.0.0" xmlns:math="http://iso.org/OTX/1.0.0/Math">

  <..>

</otx>

I want to add more namespace to the otx tag. I use a query is:

declare default element namespace "http://iso.org/OTX/1.0.0";

for $otx in collection()/otx

return replace node $otx with

<otx

 xmlns="http://iso.org/OTX/1.0.0"

 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

 xmlns:xmime="http://www.w3.org/2005/05/xmlmime"

 xmlns:diag="http://iso.org/OTX/1.0.0/DiagCom"

 xmlns:quant="http://iso.org/OTX/1.0.0/Quantities"

 xmlns:event="http://iso.org/OTX/1.0.0/Event"

 ...

  >

 

{$otx/@*}

{

   $otx/metaData, $otx/specification,$otx/adminData,$otx/imports,

   $otx/declarations, 

   $otx/validities, $otx/signatures,  

   for $p in  $otx/procedures

   let $r:= $p/realisation

   return     $p

}

</otx>

but it run very slow if the database is pretty largely. 

Please help me for a best solution.

Thanks so much!