Build the PRT
When building a PRT start at the top of the tree with the injection you want to accomplish. The injection becomes the objective of the PRT. The Objective and IO’s are in square cornered boxes and the obstacles are in round cornered boxes. This is strictly a symbol to separate the two thoughts when looking at the tree in addition to the box titles.
As a beginning point, look at your list of IO’s and determine if you can find two of them that are connected. In other words, is there one IO that must exist before another IO can exist? When you look at the IO’s ask yourself, “What must happen just before this IO can exist?” If the answer is an IO on the list then, we can make the connection with a necessity arrow. If a plausible IO does not exist then, determine what the new IO would be and write it down. Let’s make a connection from the Dome Company list.
It is not necessary to connect to the objective first. It is possible that the first connection could come from two independent IO’s. So, if we read this out loud; “In order to have Production synchronized to maximize throughput, I must have scheduling changed to a “pull” system, because Current scheduling is a push system.”
With this connection you’ll notice that IO-1 is connected to OBS-1 by the necessity arrow. All of the IO’s will always be paired with the corresponding obstacle. At this point you can ask, “Is there anything else required to be in place just before the objective?” Or, we could also ask, “What entity must exist just before IO-1 can be achieved?” Is there another IO on our list that must happen before we can change scheduling to a “Pull” system? Let’s keep building and make the connections some additional connections.
In our next posting we will complete our Prerequisite Tree (PRT) before moving on to our next TOC Thinking Process tool.