Jim Downing has kindly resurrected a doc I wrote some years ago for and Irish Government agency called Reach that is now no more. Reach's goal in life was to lay down an infrastructure to allow government agencies to integrate their IT systems and also to provide a platform on which new government services could be quickly created. It was called the PSB - Public Services Broker.
I did the initial design work and I used to call it an SOA architecture. However because that phrase is essentially meaningless I had better explain what and "SOA" means in my head and its simply this: the reliable, asynchronous exchange of business level messages using XML payloads. Tons of detail went behind that simple statement of course. It used to be all online but not so much now. Anyway, as soon as you have endpoints that need to communicate you have the question of choreography to address and that is what the Push/Pull doc was all about.