At the risk of sounding all LMGTFY, the process by which Ada was defined/selected/iterated into it's current form is
exhaustively documented. The proceedings of the DoD High Order Language Working Group is the comprehensive history, but you can find a lot of the key summary documents at
http://archive.adaic.com/pol-hist/. The Chair of the committee Col. Wm. Whitaker wrote a pretty interesting personal history of the process at
http://archive.adaic.com/pol-hist/history/holwg-93/holwg-93.....