Doctype to be included after Mapping

Hello Friends,

I am sending an IDOC to a 3rd party using HTTP adapter. I need to bring in the Doctype into the payload of the message to the 3rd party.

I required second line as

<-

http://xml.cxml.org/schemas/cXML/1.2.007/cXML.dtd">

->

so can i do using the XI Message Mapping.

Thanks,

Gaurav Jain