The Prerequisite Tree is used to surface and overcome obstacles to achieving the change towards the organization’s Goal by setting Intermediate Objectives (IOs). These IOs are sequential steps to implementing the change or steps helping to overcome or neutralize the obstacles.
The Prerequisite Tree is a necessity logic-based tree, like the Goal Tree and its building starts from the Goal or objective downwards. The objective may be the result of an injection identified in a prior Future Reality Tree (FRT). The implementation sequence starts from the bottom up to the top as each layer is dependant on the layer underneath.
The underlying IOs are the tasks required for attaining the objective. If Obstacles surface, additional IOs are required to bypass or neutralize them.
IOs are depicted in square cornered boxes while obstacles are depicted as hexagons or “stop signs”.
The graphic convention I use is the one recommended by Bill Dettmer, putting the IOs on top of the obstacles they help to overcome. The original convention is to put obstacles on a side between two IOS and link them with an arrow to the arrow linking the IOs.
The Prerequisite Tree is the preparatory work for the coming implementation action plan as well as a useful communication tool and a means to overcome fear and/or resistance to change. Obstacles may be stated in sentences starting with “yes, but…”.
The related Intermediate Objective(s) prove there is a way to neutralize, bypass or overcome the obstacle.
Obstacles may be real, not only reluctance or fear about change. The lack of a specific required know-how is a valid obstacle and the corresponding IO may be hire the needed know-how or develop it by training.