ToC Thinking Processes

Theory Of Constraints Thinking Processes from It's Not Luck by Eli Goldratt

Good overview on External Constraints Course page.

  • list 10-15 UDEs (Un Desirable Effects: problems, symptoms)

  • use Current Reality Tree to build intuition (see gmazur )

    • take 2 UDEs that are related, draw arrow to show which causes which (causality flows upward generally). If combination of multiple UDEs cause another UDE, use ellipse to group the causal arrows. If any of multiple UDE s cause another (OR instead of AND), don't use ellipse.

    • add intermediate assumptions, rules, etc. as needed to make causal change complete/accurate

    • question the tree - see Categories Of Legitimate Reservation

    • it's possible for the causal chain to loop around on itself: this is a FeedBack loop, which isn't surprising in a dynamic system

    • identify node which is Root Cause (not sure how: linked to many UDEs?)

  • use Evaporating Cloud to expose conflicts between rules/assumptions

    • start with immediate conflicting prerequisites (e.g. 2 policies are decisions which conflict with each other)

    • identify the requirement each is trying to fulfill (1 req for each)

    • identify the single shared objective of having both requirements

    • identify assumptions associated with each arrow between nodes

    • break an assumption with an "injection" which neutralizes the conflict

  • use Future Reality Tree to show impacts of changes to rules/plans

    • positively rephrase Core Problem from Current Reality Tree into DE (Desirable Effect), put at top

    • Put current reality (top of CRT) and injections (from EC) at the bottom

    • put objective (from EC) in the middle

    • build tree upward from injections to objectives to DE.

    • look for positive reinforcing loops

    • for each injection add Negative Branches (negative consequences or scenarios): for each NB add additional injections to counteract. (Check for NBs to new injections as well.)

  • use Prerequisite Tree to identify obstacles to overcome before the change can be made

    • put objective at the top

    • raise obstacles

    • for each obstacle, identify an intermediate objective to overcome it

    • sequence obstacles and IOs

  • use Transition Tree to plan the process of implementing the change.

See also Frank Patrick's series


No book that I've seen has a 100% working through of a single one of these processes. I guess that would reduce the sales of consulting and training...


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