Although I wrote in The Thin Book of Appreciative Inquiry , that you can begin applying the principles anywhere, I want to emphasize that in order to get large system change, you must engage the entire system in the effort. Grass root attempts work but only to a limited degree. Many times, assumptions are unspoken or operating at an unconscious level. Senge termed a set of working assumptions a mental model. I believe that the key to all change efforts is the surfacing and examination of working assumptions.
Reality is created in the moment and there are multiple realities.
The act of asking questions of an organization or group influences the group in some way. If we carry parts of the past forward, they should be what is best about the past. It is important to value differences. The language we use creates our reality. This set of assumptions may look reasonable to you but the application of the set may be a challenge.