SAP HR module integration with SAP PI

Hi Experts,

There is some initial discussions on using SAP PI for HR module integration. I have been asked to look for documents on such integration. Can someone help? I did not find much about this. I am aware that there are IDOCs that are used for HR functionality but what about legacy HR system. If anyone has worked or can give some good document link it would be of great help.SAP PI 7.1 or 7.3 or 7.4 anything would help.

What sort of interfaces are best suitable for HR module integration? IDOC to FILE/SFTP etc?

Thanks,

Shaibayan