When you are setting up the purchase send functionality you might want to test the generation of the XML documents before sending them to the suppliers. There is a function provided on the purchase request form that you can use to generate the cXML which will allow you to review. This is handy if you have turned off the live send in the cXML parameters and don’t have the batch job running and just want to generate the output for one purchase order.
Here is a quick overview
Refer to this post for an overview of the cXML Purchase Order Send.