This is because one of the components of the Thinking Processes is the set of logic rules that underpin the trees.
Goldratt's Categories of Legitimate Reservation CLR provide guidelines for communicating any reservations about the validity of the elements and connections within the trees see Dettmer, ; Balderstone, In the case of the PRT, it is to identify the critical elements, or obstacles, standing in the TOC practitioner's way of reaching the objective. If so, a PRT may be needed to sequence the intermediate steps to achieve it.
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If not, then a PRT will help map out the possible obstacles, the steps involved in overcoming them, and the appropriate sequence. Practitioners use the effect-cause-effect method to construct and scrutinise the details of the action plan, called the Transition Tree. Dettmer sees the FRT as a strategic tool in which major changes can be outlined. The implementation of these, however, will require complex interventions needing greater detail of actions to be taken, which is the intended use for the Transition Tree.
As such he sees the Transition Tree as an operational or tactical tool. Dettmer states that the purpose of a Transition Tree is to implement change. He says that the Transition Tree structure started off as a four-element tree, with a fifth element being added later. Dettmer feels that the use of the four or five element tree is situational. Dettmer outlines the original four elements of the Transition Tree as: 1 A condition of existing reality, 2 an unfulfilled need, 3 a specific action to be taken, and, 4 an expected effect of the integration of the preceding three.
Each succeeding level of the Tree is built upon the previous level, with the expected effect taking the place of the unfulfilled need.go here
Theory of Constraints & Strategy – An Introduction
These build progressively upward to an overall objective or desired effect. The fifth element added to the Transition Tree is: 5 the rationale for a need at the next higher level of the tree. This change was devised to better assist buy-in from those from whom the TOC practitioner requires assistance. People are often inclined to resist change without a good explanation for the background to it. Also, frequently the implementation of major change falls outside the span of control of the person designing the change initiative, so that it is important to obtain the commitment of those who have the required power to ensure implementation.
The fifth element that Goldratt has added appears to address these issues. This shows the 5 diagrams and the usual way they interconnect if used in sequence to solve a complex problem. The five stage Theory of Constraints thinking process begins with a Current Reality Tree, which diagnoses what, in the system, needs to be changed. The Evaporating Cloud is then used to gain an understanding conflict within the system environment or, as Goldratt prefers to call it, the reality that is causing the conflict.
The Evaporating Cloud also provides ideas of what can be changed to break the conflict and resolve the core problem. The Future Reality Tree takes these ideas for change and ensures the new reality created would in fact resolve the unsatisfactory systems conditions and not cause new ones. The Prerequisite Tree determines obstacles to implementation and ways to overcome them and the Transition Tree is a means by which to create a step-by-step implementation plan. The five tools can be used individually or in concert depending on the complexity of the situation that is being faced. The process allows practitioners to logically and thoroughly prepare themselves to successfully develop and implement change solutions.
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Many applications of the Thinking Processes have been published since their debut in Goldratt : there have been many examples presented in the APICS Constraints Management Symposiums, and in books such as Noreen et al , and Kendall Linking Hard and Soft: As can be seen from the above, TOC is a systems method inasmuch as a system of interest is being modeled. What distinguishes this approach from many other systems methods is that TOC does not attempt to model a complete system, but rather chooses to model only those aspects of the system which are considered pertinent to the adverse performance of the system.
The hard science presents itself in the form of the logical structures of the diagrams: viz, necessary condition logic, the sufficient cause logic, and the strict logic rules that are used to validate the cause and effect relationships of the logic trees. This is important to ensure that pertinent aspects of the problem are not omitted, and to allow correct deductions to be made.
The softer science methods are apparent in the complexity of the problems being tackled, and the softer nature of the elements of the model, such as behaviours, policies, perceptions, and a plurality of views. Links with other Systems approaches: It is interesting to note the similarities and differences with the standard "Rational Model" adopted by problem solvers from various fields, including hard-systems approaches Ackoff, In many respects the TOC method follows this apparently ideal approach, yet - in fundamental ways - it challenges it.
An excellent example is provided by The Goal Goldratt The central character, Alex Rogo, is guided on the path to turning around his under-performing factory, by the enigmatic questions of an old physics teacher of his, called Jonah. Jonah deduces, by using effect-cause-effect thinking, that Alex doesn't really understand what is driving his business, in particular the damaging effect of local performance measures that Jonah sees in evidence.
He asks Alex what the goal of his business is.
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Alex discovers that what he thought was obvious, is far from correct, so he sets out to define a clear and appropriate goal. Next he devises a set of performance measures that will serve the company at both global and local decision making levels by providing a clear indication of performance and also for helping decide which actions would be best.
Alex devises and implements his solutions, in response to Jonah's enigmatic questions, with the help of the relevant members of his staff, and the plant is saved - for the time being! The story resumes in the second novel, It's Not Luck, Goldratt One of Alex's key learning points is when he discovers that the system's performance is not predictable from the sum of its parts.
Now let us consider the Rational Model Ackoff , p13 , summarised below: 1. Identify the problem 2. Define the objectives 3. Determine the criteria 4. Structure the Problem 5. Develop Alternatives 6.
Evaluate Alternatives 7. Recommend Courses of Action 8. Implement Decisions 9. Repeat The first step, defining the problem, is what is done first in The Goal: the problem is that the plant is not making enough money and is about to be closed. Alex then finds that he needs to define the goal or objective, then decide on how to measure performance relative to that goal.
This is equivalent to defining criteria, yardsticks, and deciding on relative priorities between criteria. Thus the two methods are consistent in the first three steps.
The next steps in the Five Focusing Steps are to identify the constraint that is limiting the system's performance, and exploit the constraint: to ensure it is working to give the maximum benefit to the system. Essentially here we consider the current use of the constraint, identify the reasons for the constraint and identify alternative actions and their impact on the constraint. A number of specific and generic suggestions for action are contained in The Goal and in The Race, Goldratt and Fox, The rational model ends with implementation, though actual modeling approaches seldom give any guidelines on this step: in The Goal, this step is an integral part of the whole process.
The final step of going back to the start in an iterative process is common to both methods in theory, at least. So there are many similarities on the surface between the logical flow of events between the two approaches, and one could ask whether Goldratt had added anything new. However there are a number of significant differences.
Harnessing resistance: using the theory of constraints to assist change management
Goldratt's five focusing steps methods leads to a streamlined approach, by focusing on the key role played by the constraints. The Socratic method he uses, especially in his novels, promotes a self- help approach, which wins over people far more easily than the prescriptive approach inherent in the rational model. They are finding it out for themselves in a journey of discovery; no-one is telling them what to do!
The solutions to the problems are generated by people within the organisation - not by outside experts. Here what matters is whether the actions will improve the output of the system, not on which is best. So this is perhaps more of a satisficing approach than a rational optimising approach. Goldratt demonstrates very clearly in his novels the dire consequences of not being clear about goals and of choosing inappropriate measures: the motivation for change is strong and clear.
Finally, the process is one of on-going improvement, not a one-off solution. The Thinking Processes seem to provide even more significant differences, while still adopting a seemingly rational process. Goldratt is starting from the assumption that we are usually far better at saying what's wrong, than what's right. Thus the first step in the process, building the Current Reality Tree, starts by listing the undesirable things about our reality, the symptoms, that are evidence of a system that is under- performing. Kendall states that the three pillars of success are policies, performance measures and training.
Conversely these are the most common root causes of problems. These in turn are probably the results of unclear goals, or of multiple goals with unclear priorities between them. Or if our goal is clear and well-defined, then we can find ourselves being driven in two opposing directions, due to inappropriate local measures in different departments. This conflict is well captured and resolved using the Evaporating Cloud. Once goals and performance measures have been agreed upon, it is necessary to identify options, and evaluate them, before planning implementation.
The Evaporating Cloud helps us to identify possible actions by challenging the assumptions which underpin the conflict, and selecting the ideas that we think hold most promise. Next the Future Reality Tree predicts the impact of those ideas, if implemented, allowing an assessment of their effectiveness. The FRT also provides a first step in testing implementation issues. Finally the Prerequisite and Transition Trees are used to explore further implementation issues. The process theoretically is repeated if necessary, though this is rather less likely with the TP's than with the Five Focusing Steps method, because the TP's are such an exhaustive and exhausting process!
The changes arising from the use of the TP's tend to be more tailored than those arising from Five Focusing Steps, as the TP's encourage practitioners to develop their own solutions to difficult problems, and provide the necessary tools to do so. For example the Evaporating Cloud is excellent for generating new ideas for solving old problems, particularly behaviours or policies that are preventing a solution.
The tools facilitate teamwork, both in the way they are used, and through the provision of the CLR. They encourage a systems view, particularly by understanding that seemingly disparate problems are often the result of the impacts and inter-relationships of some common root causes, which if dealt with, will lead to a marked improvement in the system's performance. Conclusions: Despite its origins as a manufacturing methodology, Goldratt's Theory of Constraints TOC methodology can now be regarded as a systems methodology that links elements of both soft and hard systems methods.
These comprise a suite of logic trees that provide a roadmap for change, guiding the user through the decision making process of problem structuring, problem identification, solution building, identification of barriers to be overcome, and implementation of the solution. A set of logic rules, called the Categories of Legitimate Reservation, provide the analytical rigour usually associated with hard scientific approaches.
The similarities and differences between TOC and other systems methods, are discussed. In particular, the TOC method is seen to focus on the problems currently being experienced, the most likely cause-and-effect relationships leading to these, and the best course of action to remove them, rather than aiming to model the entire system. The TOC methods also have much in common with the steps laid down in the Rational Model of decision-making. However, there are marked differences in the underlying assumptions, and methods used in the intervention process.
References: Ackoff, R. The Art of Problem Solving, Wiley. Balderstone, S. Coman, A. Cox, J.
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