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Categories of Legitimate Reservation (CLR) is a tool used to verify the validity of causal relationships. It is a set of 8 categories which are used to identify the common mistakes in the cause and effect statements like those in 5 Why or Fishbone Analysis. This tool was developed by Dr. Eliyahu Goldratt as a part of Theory of Constraints (TOC).


An application-oriented question on the topic along with responses can be seen below. The best answer was provided by Nethaji on 17th May 2024.


Applause for all the respondents - Amol Ingole, Nethaji.


Q 669What are the Categories of Legitimate Reservation and how can they be applied to the Fishbone diagram?


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Vishwadeep Khatri
This post was recognized by Vishwadeep Khatri!

"Excellent response, Nethaji."

Yarra_Nethaji was awarded the badge 'Superstar' and 50 points.

Categories of legitimate reservations:

  • The Fishbone diagram (Cause-effect) was developed by Kaoru Ishikawa. This Diagram will explain the relation ship between X’s versus single Y. Categories used are Man, Machine, Method, Material, Measurements, Mother nature. During the project as a team along with SMEs we sit together find out the relationship between X’s and Y. In general these logical relationship based on experience, assumptions. Hence there is no proper way to validate(logical) connections. However, there is a powerful tool in theory of constraints i.e. Categories of Legitimate Reservations. These rules developed to verify and validate the cause -and -effect relationship
  • Goldratt developed these logical rules names as Categories of Legitimate Reservations. The main purpose of CLR to check the logic of our ideas with the others logic. These categories provide a methodology to pinpointing errors in our & other person thinking. In other words, CLRs are type of doubt (self or other) might have. The doubts or concerns may pertain to logic or the reason discussed.  The below listed are the type of CLRs
    • Clarity (Level-1)
    • Entity of existence (Level-2)
    • Causality Existence (Level-2)
    • Cause insufficiency (Level-3)
    • Additional cause (Level-3)
    • Cause-effect reversal (Level-3)
    • Predicted effect existence (Level-3)
    • Tautology (Level-3)
  • Clarity – It gives understanding the between the cause & effect. This is the first reservation, which is considered. While preparing and presenting, we seek clarity from each member participated in the session about the cause-effect relationship. This is very important; we should not make the cause-effect diagram just for sake of presenting to senior management or the project completion. The quality of the cause will impact the subsequent steps in analysis. The clarity reservation gives chance to each member to understand the what effect we are discussing, what causes we are putting on the diagram. if someone who are not know about the diagram, can they understand by seeing it. If not, they can reach out to the presenter for clarification.
  • Entity Existence: If the relationship is not clarified by first level, we need to use this rule for validation. In this step, we can verify whether the given relationship is existed in the real process. Because during team exercise, people will confuse and provide the relationship which are assumptions, but not the realities. For example, Car milage(Y) has a relationship with driver age(X). This kind of relationship can be dropped off after looking into this rule.
  • Causality Existence:  In this level 2 rule, we will validate the given cause is really responsible for the effect. Some time, people tend to give the causes which are closely associated/correlated with the effect. For example, we are doing the fishbone for low bulk (Bulk = calliper/gsm) of a paper. The two causes mentioned is grammage of the paper and calliper of the paper. But these two are associated. Because if the grammage increases, calliper will increase. To take one of the causes, we need to have much stronger evidence
  • Cause insufficiency: In this levl-3 rule, we will validate that given cause is responsible alone to the effect and it is combined with another cause to create the particular effect. Reference to the previous examples of paper bulk, the bulk is low is due to the paper is pressed between rolls. But loading the rolls is insufficient. The load is more than the required is combined to creating the low bulk. Which mean higher press load will give lower bulk
  • Additional Cause:  In this level-3 rules, we will find/validate that is there any other independent causes are the to give the same effect. Reference to previous example of bulk, along with higher press load, higher moisture will also impact the lower bulk. Another example is employee morale goes down when we cut the staff, but another independent cause is removing/reducing the benefits
  • Cause-Effect reversal:  In this level-3 rules, we will find/validate that is the arrow drawn between cause & effect is correct, which means some time the cause written is actually effect. For example, I spent less family time(cause) for long working hours(effect). But in it should be reverse. i.e. I spent less time with family(effect) due to long working hours(Cause)
  • Predicted effect existence: In this level-3 rule, we will find/validate that is the given cause will lead to any other effect. If not, then we can go for the additional cause. For example, in health report we got high cholesterol (effect). My diet is having more oily foods (Cause). But this also might have another effect is (fatty liver). If the additional predicted effects are also observed, it will give confidence about the causality identified initially. But if the predicted effects are not observed, then we can look for additional causes.
  • Tautology: This is also known as circular logic. In this level-3, we often check if the effect is the only and inadequate evidence provided for the given cause. People sometimes don’t examine their beliefs, when we verify for a cause, they often give the cause with different words. Some of the examples are
    • Machine produce highest quantity, because it is only machine available with higher capacity
    • Japanese trains come on time, because they are punctual
    • Motor fail very frequently, because it repaired many times
    • The additional features given in customer which is free that cost nothing at all
  • Each category (Rules) is used as a checkpoint to test the validity and logical relationship while preparing & discussing the cause-effect diagram. These rules provide a systematic way to scrutinize and validate the logical structure of a problem and its solution, enhancing decision-making.
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The Categories of Legitimate Reservation (CLR) are rules designed to verify the validity, logic and soundness of cause-and-effect relationships within a problem-solving framework called the Theory of Constraints (TOC) Thinking Processes (TP).

These categories act as a quality checker for logic trees and diagrams, ensuring clear and accurate cause-and-effect connections.

There are eight CLRs, categorized into three levels that delve deeper into the logic structure:

  • Level 1: Clarity and Existence
    • Clarity Reservation: Ensures clear and unambiguous wording of entities (boxes) in the Fishbone diagram. Each entity should represent a single, well-defined concept.
    • Entity Existence Reservation: It questions the actual existence of the entity within the scope of the problem you're analysing.
  • Level 2: Causality
    • Causality Existence Reservation: Challenges the cause-and-effect relationship between entities. Does one truly cause the other, or is it just a correlation?
    • Cause Sufficiency Reservation: Asks if the identified cause is truly enough to bring about the effect. Are there other contributing factors?
    • Additional Cause Reservation: Examines if there might be other, unidentified causes leading to the same effect.
  • Level 3: Structure
    • Cause-Effect Reversal Reservation: Checks if the cause and effect haven't been accidentally reversed in the diagram.
    • Indirect Effects Reservation: Ensures the diagram captures all the necessary steps leading from cause to effect. Are there missing intermediate effects?
    • Tautology Reservation: Identifies redundant statements in the diagram that don't add new information.

Applying these categories helps ensure the fishbone diagram accurately represents cause-and-effect relationships, leading to better problem-solving and root cause analysis.

 They are widely used across various industries, including manufacturing, healthcare, quality management, and project management.




Example with Food Manufacturing Industry:

As a food manufacturer, you must solve manufacturing-related problems quickly to avoid hazards, contamination, or operational inefficiencies. Categories of Legitimate Reservation helps to identify the cause of a complicated problem or inefficiency in your facility.

To uncover potential root causes food manufacturer (production managers) must ask several Why’s.

Manufacturing plant machines & related technologies are essential tools to grow the production capacity ultimately resulting into growth of business.

However, any problems or issues related to machines may increase potential threat for production & pre-defined processes.


Machines overheat several times a week which need to be shutdown for quality & safety concerns.

Instead of machines shutdown we need to find root cause of issue with help of Whys.

1)    Why machines overheat around 2 pm each day?


(answer: Climate surrounding manufacturing plant is too hot)

2)    Why the climate surrounding manufacturing plant is too hot?

(answer: Plant facility manager refuses to lower building temperature)

3)    Why? (answer: some ingredients become too cold at input)

4)    Why can’t those ingredients be kept warm another way? (answer: we have no portable coolers space)

5)    Why? (answer: no good reason).

Solution: put the ingredients in portable coolers and lower the building temperature to prevent the machines from overheating.

Similarly, expand the analysis by asking more Why’s if the answers fail to resolve root cause of problem.




Factors affecting in Food Manufacturing:

1.     Machinery

2.     Methods

3.     People

4.     Equipment

Consider the scenario below in which 5% of a cake manufacturer’s batches of double chocolate chip cake are burnt. Asking the “Whys” will likely NOT uncover the problem this complex, so many manufacturers use the fishbone diagram and ask ‘why?’ in that context.





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Excellent answer from Nethaji. The answer very clearly explains how CLR can help us make effective fishbone diagrams.


P.S. - Many participants had responded to this question, however only 2 answers were published as the other answers were incorrect.

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