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Process Control Loop with Data Feedback Routes
Balancing Process/Loop and Data Feedback Routes
Combined with reinforcing loops, balancing processes form the building blocks of dynamic systems. Balancing processes seek equilibrium: They try to bring things to a desired state and keep them there. They also limit and constrain change generated by reinforcing processes. A balancing loop in a causal loop diagram depicts a balancing process.
Articulating Reality
Causal loop diagrams provide a language for articulating our understanding
of the dynamic, interconnected nature of our world. We can think
of them as sentences which are constructed by linking together key
variables and indicating the causal relationships be-----tw-een
them. By stringing together several loops, we can create a coherent
story about a particular problem or issue.
- Theme Selection. Creating causal loop diagrams is
not an end unto itself, but part of a process of articulating and
communicating deeper insights about complex issues. It is pointless
to begin creating a causal loop diagram without having selected
a theme or issue that you wish to understand better. "To understand
the implications of chang-ing from a technology-driven to a marketing-oriented
strategy," for ex-ample, is a better theme than "to better
understand our strategic planning process."
- Time Horizon. It is also helpful to determine an appropriate
time horizon for the issue-one long enough to see the dynamics play
out. For a change in corporate strategy, the time horizon may span
several years, while a change in advertising campaigns may be on
the order of months.
Time itself should not be included as a causal agent, however. After
a heavy rainfall a river level steadily rises over time, but we
would not attribute it to the passage of time. You need to identify
what is actual driv-ing the change. In manufacturing, for example,
costs of a new product often decline over time. It would be incorrect,
however, to draw a causal connection between time and unit costs.
Instead, process improvements and learning curve effects are likely
causal forces.
- Behavior Over Time Charts. Identifying and drawing
out the behavior over time of key variables is an important first
step toward articulating the current understanding of the system.
Drawing out future behavior means taking a risk-the risk of being
wrong. The fact is, any projection of the future will be wrong,
but by making it explicit, we can test our assumptions and uncover
inconsistencies that may otherwise never get surfaced. For example,
drawing projections of steady productivity growth while training
dollars are shrinking raises the question "If training is not
driving productivity, what will?" The behavior over time diagram
also points out key variables that should be included in the
diagram, such as training budget and productivity. Your diagram
should try to capture the structure that will produce the projected
behavior.
- Boundary Issue. How do you know when to stop adding
to your diagram? If you don't stay focused on the issue, you may
quickly find yourself overwhelmed by the number of connections possible.
Remember, you are not trying to draw out the whole system-only what
is critical to the theme being addressed. When in doubt about including
something, ask, "If I were to double or halve this variable,
would it have a significant effect on the issue I am mapping?" If not, it probably can be omitted.
- Level of Aggregation. How detailed should the diagram
be? Again, this should be determined by the issue itself. The time
horizon also can help determine how detailed the variables need
to be. If the time horizon is on the order of weeks (fluctuations
on the production line), variables that change slowly over a period
of many years may be assumed to be constant (such as building new
factories). As a rule of thumb, the variables should not describe
specific events (a broken pump); they should represent patterns
of behavior (pump breakdowns throughout the plant).
- Significant Delays. Make sure to identify which (if
any) links have significant delays relative to the rest of the diagram.
Delays are important because they are often the source of imbalances
that accumulate in the system. It may help to visualize pressures
building up in the system by viewing the delay connection as a relief
valve that either opens slowly as pressure builds or opens abruptly
when the pressure hits a critical value. An example of this might
be a delay between long work hours and burnout: after sustained
periods of working 60+ hours per week, a sudden collapse might occur
in the form of burnout.
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