System Dynamics Pitfalls and Pointers
Time in System Dynamics Models
System dynamics modelling is time-domain modelling in which we set
out to formulate and analyse how cause-and-effect relationships work to
produce variations over time. Building rigorous, reliable and meaningful system
dynamics models demands a sound understanding of time, and how
to represent the passing of time in models. In system
dynamics modelling, we are interested in five distinct representations of
- Time Horizon—length of a planned simulation, from a defined start
time to a defined stop time.
- Time Status—current simulation time, which
will lie somewhere between the defined start and the defined
stop time, and includes the start and stop times.
- Elapsed Time—time
elapsed since the current simulation commenced.
- Time Unit—the chosen unit of
time used throughout the simulation for the purpose of making
calculations and providing reports.
- Delta Time, dt or Timestep—the increment of
time by which the current simulation progresses once of a
given single cycle of calculations has been completed.
The following defines
the meaning of time and how to correctly represent it
in system dynamics models .
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