Prerequisite Tree Processes (PRT)

The thinking processes are very flexible and are used in a number of different ways.

Most commonly the Cloud and the PRT are used together to deal with day to day problem and ambitious objectives.

The prerequisite process is one of the fastest processes available to develop a solid implementation plan either working with a small team or individually.

Prerequisite Tree (PRT)

The prerequisite process is used to break down larger changes or implementation steps into logical smaller steps. The outcome of the prerequisite process is a Prerequisite Tree (PRT) as shown in the diagram below.

 A Full Prerequisite Tree

The diagram to the left shows a full Prerequisite Tree. At the TOP of the tree are two square corner boxes with the letters Inj in them. Inj is short for Injection. An Injection in TOC terms is something that needs to be implemented as part of a TOC application. Injections are usually non trivial changes. In this case the Inj are the objectives of this PRT. Below these boxes the intermediate objectives (IO) needed have been identified by surfacing the obstacles (Obs) that block the implementation of the Injections. Each IO in the tree is necessary to overcome one of the obstacles.

The PRT is often the basis for a project network. Each IO being broken down again into smaller steps and into the actions needed to achieve it.

Today the full PRT is not often drawn. Rather an IO map is produced without showing the obstacles.

PRT Structure Logic.

The PRT tree or IO map is constructed around necessary conditions. In the diagram above the left hand Injection (Inj) cannot be achieved without the IO below it being achieved. Likewise this IO cannot be achieved without the two IO below it first being achieved. The sequence that these IO need to be achieved is identified by considering the obstacles. The left hand Injection cannot be achieved because of the top obstacle on the left hand side of the diagram. The obstacle is overcome by the IO below it. To check that the PRT structure is sound we use our intuition developed by our experience, knowledge and understanding of the situation. To utilise our intuition we read down the structure in this way: In order to have the Injection (Inj) we must have the Intermediate Objective (IO) because of the Obstacle (Obs). 

Simple Example

Objective: We have a new office block. 
What will block this objective? 

Obstacle 1: The site is covered in trees bushes and rubbish. 

What will overcome the obstacle? 

Intermediate Objective 1: The site is clear of all obstructions to building works. 

Obstacle 2: The ground cannot support walls. What will overcome the obstacle? 

Intermediate Objective 2: There are foundations.

How to reveal the IO sequence - look for two IO that appear connected, referring to the obstacles and using your intuition decide which must be achieved first, place it below the other (see the PRT excerpt tree below).

How to check the logical IO sequence? Read adding the phrases or similar phrase/word shown in italics.

In order that There are foundations (IO 2), The site must be clear of all obstructions to building works (IO 1), because The site is covered in trees bushes and rubbish (Obs 1).

How to build a PRT

1. State clearly the objective to be achieved.
2. Surface the main obstacles that will block the achievement of the objective identified in 1 above. (it is useful to number each obstacle)
3. Identify what has to be achieved to overcome each obstacle. It is highly likely that some IO may overcome more than one obstacle. (It is useful to number each IO)
4. Map the IO or build a full PRT.
5. Convert the IO map into a project plan.

Modifications for working in a team. 

Step 2

2.1 Ask the individuals in the team to list on paper the obstacles that they see will block the objective.

2.2 Ask in turn each member of the team to share one obstacle from their list, write each obstacle  on a flip chart/white board or other device such that everyone can see the obstacles being raised. Continue going around the team members until all the significant obstacles have been shared and listed. (it is likely that some of the obstacles on any team members list are raised by other team members - if this is the case they should move onto raise a different obstacle).

2.3 Group any obstacles that are similar - combine identical obstacles raised by different individual into an agreed sentence.

Step 3

3.1 Ask each member of the team in turn to suggest what has to be achieved in order to overcome one obstacles they raised. Continue this process until every obstacle has an IO.

3.2 Group any IO that are similar and combine identical IO raised at different times or by different team members into an agreed common sentence.

Step 4 

4.1 List each IO on a sticky note or another medium that will allow the team to arrange these on a white board or wall or another device such that each IO can be moved around independently.

4.2 Have the team gather around the device being used and map the IO.  Facilitate this process using the logic checking process outlined above.