A big topic, fairly poorly documented by the OpenAM project itself. To the rescue comes Filip Czaja, a systems architect in Poland, with this excellent series finally making everything clear.
There’s metaphorical gold in the pages of Filip Czaja’s blog, especially for anyone who needs to understand how OpenAM federation works in order to keep their children clothed and fed. The series is entitled:
and here are separate links to each of its parts (I recommend you read them all, even if you’re just a humble sysadmin like me):