What is a Prerequisite Tree (PrT)?

A long journey needs its milestones

Now the tactical objectives of our improvements efforts are at last clearly defined; we need to implement the injections.  Simply the future reality tree has logically shown that once the injections are implemented the desired outcome all the strategic objectives will be accomplished.

Implementing the injections if not a trivial task.  Lets not forget that at lest one of the injections is a breakthrough a departure from the current prevailing tradition. Thus it is usually necessary to break the implementation task into smaller increments.

For this we use the prerequisites tree.  Starting with the obstacles that we expect we’ll encounter the necessary milestones – the intermediate objectives are verbalised.  Each obstacle gives rise to an intermediate objective one we assess will be sufficient to overcome the corresponding obstacle.

To complete this step the intermediate objectives need to be sequenced, i.e.: which one is first, which ones can be accomplished n parallel etc. The connections are provided by the fact that any time dependency is due to the need to overcome an obstacle.

The power of the prerequisite tree stems from the fact that it doesn’t ignore the obstacles, on the contrary they are used as the main vehicle for this entire setup.