Theory of Constraints

By | December 10, 2014

The definition of constraint in English:


A limitation or restriction


The systems that we work in often face limitations or restrictions. These can stop us efficiently reaching our goals.


What is the Theory of Constraints?

The Theory of Constraints, created by Eliyahu M. Goldratt and illustrated in his book The Goal, is a framework for identifying where constraints are in a system and then going through a process to improve the situation.

The Goal uses a manufacturing plant to illustrate the Theory of Constraints, however it can be applied to any process or system in order to eradicate limiting factors, and consequently improve the system’s throughput.

The five focussing steps

In short, the process for identifying and eliminating a constraint is known as ‘the five focussing steps’. These are as follows:

1. Identify the constraint.

The first step is to find the single point in our system that is most limiting the rate at which we complete our work in order to meet our goal.

Let’s take an example of a software development team: we may identify that manual testing is the point where work is backing up and at which work is slowest to flow through. This is our constraint.

2. Decide how to exploit the constraint.

The next step is to ensure that the stage in our process where the constraint is identified is working at maximum capacity.

Example: we ensure that the people involved in the testing activity are solely working on this.

3. Subordinate and synchronize everything else to the above decisions.

This step requires that all other stages in our process are aligned with the constraint. This means that all other stages are working in a way which reduces the load that is put on the constraint.

Example: ensure that we are using unit tests and that each work item is code reviewed by 2 other people before it goes to test.

4. Elevate the performance of the constraint.

This step is required if the constraint still exists even after we have gone through the previous three steps. We would keep working through this stage until the constraint stops being a constraint. This may involve financial investment to help alleviate the issue.

Example: we may look to try and bring the testing activity forward in the process and in the most extreme circumstance we may even look to recruit additional people to take part in the testing activity.

5. If in any of the above steps the constraint has shifted, go back to Step 1

Goldratt describes the Theory of Constraints and its five focussing steps as ‘A process of ongoing improvement’ (see The Goal: A Process of Ongoing Improvement). This means that once a constraint has been broken, we immediately move on to try and break the next constraint. Goldratt also says we should ‘not allow inertia to cause a system’s constraint.’

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