at the core, enterprise architecture is very simple: it starts with the idea that one should plan technology purchases and development ahead of time and -- here's the important part -- that the business people, not technology people, should determine what is needed (the requirements).
EDA is more a manifestation of finite state machines going all the way back to Alan Turing. Old_State + Event = Some_Action + New_State. It is the simplest, yet most powerful way to design robust systems. I only wish more people would give it due consideration.
A very old implementation example is I/O interrupts (hardware events) for asynchronous I/O - real time event handling which enabled multitasking operating systems.
Many want to use web services for everything now and at times it is hard to convince people that other messaging schemes and standards are a better fit for some problems.