Prerequisite Tree (PRT)
In a previous posting we presented the Future Reality Tree (FRT). The FRT is the final step in determining a possible answer to the question; “What to change to.” The FRT was used to test possible injection(s) to help solve the problem. Once an answer has been isolated that appears to create the Desired Effects for the future we must determine how best to implement the idea. The PRT allows for the logical links, and thinking, to determine what steps will be necessary to implement the idea (injection) and make it a reality. The PRT becomes the transition tool to move the thinking from “What to change to” to “How to cause the change to happen.
Prerequisite Tree (PRT)
The PRT is necessity based with its logic. In other words, when reading the PRT we revert back to “In order to have entity A…. I must have entity B.” With the PRT we are trying to surface, and overcome, the obstacles (reasons) about “WHY” we can’t implement our injection (idea) right now. What stands in the way of making our good idea a reality? What things must be overcome to implement the new idea? With the PRT we will surface the obstacles that could/will stop us from implementing the injection and develop the Intermediate Objectives (IO) that will allow us to overcome the obstacles. The IO’s will be the entities that must exist to overcome and remove the obstacles.
The PRT provides a structure that defines the intrinsic order of the tasks that need to be completed to implement the idea. Using the previous thinking tools we have already surfaced a root cause with the CRT; determined, and solved, a conflict with the CRD by surfacing a plausible injection; and tested the selected injection using the FRT to make sure we get the desired effects we are looking for. Now we will use the PRT to determine the required tasks that will be part of the implementation plan. In our case, the PRT will be constructed as a continuation of a full systems thinking process analysis for the Dome Company.
Building the PRT
When you look at the selected injection from the FRT you might be thinking to yourself, “It’s a great idea but, how do I make that happen?” The PRT will allow us to systematically divide this major task into a set of interdependent smaller tasks. We will use the PRT to sequence the task completions based on the time dependencies. In other words, which task do I do first? Which one is second? Which one is third? etc. The output of the PRT is a structured plan that defines the tasks and determines the intrinsic order for completion.
The PRT has three elements.1. Objective. The objective is what we want to ultimately achieve with this process. It’s the reason we are doing a PRT. In our case, the objective would be the selected injection from the FRT that we want to implement.
2. Intermediate Objectives (IO). The IO’s are the ideas that will help us overcome and remove the obstacles that exist. It is possible that a single IO can overcome more than one obstacle.
3. Obstacles. An entity that does, will or can block the achievement of the PRT objective. Something that currently exists that could/will prevent you from achieving the injection.
The first step to develop a PRT is to list as many obstacles as you can think of that will/could block you from achieving the PRT objective. In the case of the Dome Company our objective is: “Production is synchronized to maximize throughput.”
Once you have identified the list of obstacles it’s time to identify the Intermediate Objectives to counter the effects of the obstacles. Remember: an IO is an entity that if it existed then, the obstacle would no longer be a problem.
The IO list now gives us the task list for those entities that must be completed to overcome the obstacles. This list is not intended to be a complete list but, rather a starting point. It is highly likely that additional obstacles and IO’s will be surfaced when you build the PRT. In our next posting we will continue building our PRT.