Is there any RTC Java API architecutre or design diagram?

Recently I am creating some event handling following up action, which will use RTC server side API.
I used Plain Java API before from client, I find the API is different for server side and client side.
I can searched more useful information and code segment from this forum, another way, some one could told me the related class and I can search more things in SDK source code.

But I do not have a whole picture of the RTC API Design, and just know the a little about ItemService, ItemHandle, fetchItem().
Any one or any where has the total picture of API and SDK, I think it will be useful for most of the users.

Thanks!