Thinking Process Tools

The Primary Tools of the Theory of Constraints Thinking Processes

Tools to take you from Symptoms to a solution at the core problem level, and corresponding action plan

To give this topic some context, many companies using just the Synchronous Manufacturing application of the Theory of Constraints will not even be aware there are such things as the TOC Thinking Processes.

The Thinking Processes lie behind the development of most applications of the TOC, and they lie behind a lot of the analysis and planning that a TOC consultant will perform in connection with an implementation – but they are not always overt.


While the original Thinking Processes that were developed in 1988 – 1994 continue to evolve, five basic Thinking Processes remain at the heart of the Theory of Constraints … but a new Tool, introduced in 2006, has also proven extraordinarily effective when the intention is not to eliminate problems but rather to aim for a specific highly desirable “effect.”

Each Thinking Process includes the use of a particular form of logic diagram.

  • Three of the Theory of Constraints Thinking Processes use a form of logic called “Effect-Cause-Effect.” These processes focus on sufficiency i.e. ensuring that all elements of an analysis or plan are in place.
  • Two processes use necessary conditions, rather than sufficiency. These home in on making sure that all the essential elements of an analysis or a plan are in place.

In combination, any solution resulting from these processes is virtually guaranteed a high degree of validity.

Current Reality Tree (CRT)

The CRT uses Effect-Cause-Effect logic, and can be used for several related purposes in a Theory of Constraints context.

  • To connect a set of seemingly unrelated problems using Cause-Effect connections and gain a clearer picture of what is really going on. The CRT often makes sense out of “problem soup” – a great asset of the Theory of Constraints perspective.
  • To analyze a set of symptoms and uncover a deep-rooted core problem that is causing most or all of them. Again, the concept of a core problem is fundamental to the Theory of Constraints technology.
  • To confirm that a problem thought to be a core problem, truly is responsible for the host of symptoms for which a common cause is being sought. This is by far the most common use of this technique in the past 10 years.

Variations of the CRT have been developed over the years to meet specific needs, including for example, the “Communication Current Reality Tree.”

Evaporating Cloud (sometimes called “Conflict Diagram”)

Dr. Goldratt (Eli Goldratt, or Eliyahu M. Goldratt) named this logic diagram based on a scene from the book Illusions, by Richard Bach. A bit whimsical, but what the heck – he’s the inventor.

You can use the Evaporating Cloud diagram to document a conflict in such a way that necessary conditions are defined, assumptions can be surfaced and an opening found for a win/win solution that simply “evaporates” the conflict. This win/win, outside-the-box solution is again characteristic of the Theory of Constraints approach to analysis and planning.

The technique is extraordinary flexible, adaptable (with some specific guidelines) to many different situations – from negotiation, for example, to overcoming deep-rooted personal conflicts.

Future Reality Tree (FRT)

This Effect-Cause-Effect diagram Thinking Process, one of the most constructive in the Theory of Constraints suite, also has a variety of uses.

  • To help ensure that all the elements of a solution are present, therefore offering a high degree of assurance that a “good idea” will indeed generate the desired outcomes.
  • To help ensure that the negative side effects that can arise from even the best ideas, are identified in advance and pre-empted.
  • To check where an action or decision might lead.
  • To surface “reservations” in someone’s idea or plan, such that the outcome is a stronger idea or plan but achieved in a manner that does not imply criticism and indeed creates the feeling of “you and I against the problem.”

The last one on this list is by far the most common use of this Theory of Constraints technique in recent years.

Prerequisite Tree (PRT)

Often, the obstacles to achieving something appear so big that it makes the objective seem beyond reach. Or at least, to make the path so difficult that it is not easy even to see where to start.

The Prerequisite Tree is a device for forcing out all the obstacles, and identifying ways around or through the obstacles, with the outcome being a clear-cut road map to follow. Many Theory of Constraints experts use this tool (and some variations) as a mainstay of all their strategic planning and implementation work.

Teams find this a particularly useful tool, depicting the big-picture of how they are going to get where they are going, with no ambiguity as to who is responsible for what.

Transition Tree (TT)

Another Theory of Constraints Effect-Cause-Effect diagram, the Transition Tree is used to develop a detailed action plan of precisely what must happen, in time-sequenced, cause-effect detail, in order to have a high degree of assurance that the desired outcomes will be achieved in reality. A simple, powerful tool to ensure that not only the “What” but the “Why” of a series of actions is clear to everyone associated with a plan.

The Strategy & Tactics Tree is a very different concept … it has become the focal point of implementations where the target is a very aggressive level of sales anbd profit growth, rather than the elimination of performance problems with improved performance.

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