This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
ATG is a commercial entity. Why don't you use the documentation that shipped with their product? If you don't have that, contact ATG. I'm sure they can get their paying customers the information they need much faster than anyone here could.
Go to www.atg.com, click on the small "developer" link at the bottom right-hand corner. After you log-in (I am not sure of you can register if you're not an actual customer/client), you will see a menu on the left-hand side. Go to "Product Resources" -> "Product Manuals". Select your ATG version, and there you have it.
Their site/searh is soooo slow online. You should have a local copy on your box. Contact your marketing/technical contact from ATG and they should provide you with the documentation.