PI 7.3: consume webservice using SOAP

Dear experts,

I have to consume a webservice with SAP PI 7.3. The offered webservice uses SOAP protocol.

One of our customers offers a webservice that provides purchase orders and I have to map

those to iDoc ORDERS.ORDERS05.

I have gone through:

http://scn.sap.com/people/siva.maranani/blog/2005/03/01/testing-xi-exposed-web-services

http://scn.sap.com/people/siva.maranani/blog/2005/09/03/invoke-webservices-using-sapxi

http://scn.sap.com/people/shabarish.vijayakumar/blog/2006/03/23/rfc--xi--webservice--a-complete-walkthrough-part-1

http://scn.sap.com/people/shabarish.vijayakumar/blog/2006/03/28/rfc--xi--webservice--a-complete-walkthrough-part-2

From what I understand I need an RFC that calls the webservice through PI.

"RFC -> SAP PI -> webservice".

- So to regularly check the webservice for new orders do I have to create a job in SAP ERP that triggers a report with my RFC?

- Are there other possibilities to call a webservice regularly using SAP and SAP PI?

- Do I need a Sender Adapter to send the webservice response to PI -> RFC?

- How do I map the webservice response to an iDoc ORDERS.ORDERS05?

Thank you very much for your input on this and best regards,

Peter