Scenario to get orders thru Web Service

Hi all

I have a question about how to best implement the following scenario with XI (and BPM?):

An external system provides a Web Service with the following methods: (1) getListOfOrders and (2) getOrderDetail. I need to invoke the first method getListOfOrders to retrieve a list of relevant order numbers with which I call the second method to retrieve the details of each relevant order. With the details of each relevant order I get thru the Web Service, I need to create an IDoc ORDERS05 to be sent to the SAP R/3 backend system for processing.

What would be the best way to implement such a scenario using XI? Should I use BPM for that? How then should I trigger the BPM process periodically?

I would appreciate some feedback (or even examples) if anybody has done such a scenario or know how to implement it.

Regards,

Daniel