XML as Data Source for Report Model

Hi,
I am very new to Reporting services, and am currently evaluating implementing it in my organisation. I have read that you can use an xml document as the source for a report, but i dont seem to be able to set up xml as the source for a report model. Is this normal? I have read through the help files, and cant find much info on it. Any tips, or suggestions of other places to look would be greatly appreciated!

Cheers,
Ben

'I reject your reality and substitute my own' - Adam Savage