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Simulate a Model
From SystemsWiki
There are times when insights can be gained just from understanding the structure of a model. And then there are times when the most valuable insights can only be uncovered through an understanding of the dynamic nature of the model.
This segment will guide you through several modules to provide you with sufficient understanding to investigate the dynamic nature of your models. While you might expect this to be a dry boring section, hopefully there will be a few unexpected eye openers in here.
Contents |
[edit] Components
- The Software - This module covers downloading the software, getting it installed on your computer as well as becoming familiar with the major facets of the software working environment.
- Sketch a Model - To familiarize you with the most frequently used tools within MapSys you will construct a sketch for a bathtub model.
- Setup the Model - In this module you will transform your sketch into a model ready for a simulation. To run a simulation the elements of a sketch must have equations and values associated with certain aspects of the elements. You'll become familiar with those in this module.
- Simulate the Model - Run a simulation of the bathtub model, consider the output, and become familiar with other output options.
- Savings Account - The Savings Account is used to present the last two elements of a model and discover the emergent characteristic of growth.
- Savings Account Continued - This module extends the elements of the Savings Account model and uses it to investigate why we're not all rich.
- Project Completion - The Project Completion module is used as a vehicle to introduce negative feedback and the characteristic of balance.
[edit] Summary
It is hoped that your walk through the modules of the Simulation segment has provided you with some interesting ah-ha's. There are many more to follow. Here is a summary of what was surfaced in these modules.
[edit] Systems
- Models are representations of reality intended to promote understanding. Whether a model is a good model or not depends on how well it serves its intended purpose of promoting understanding. Remember that all models are false though some models are useful. Models are created using four primitives:
- Stock: an amount of something which increases or decreases over time as a result of a flow.
- Flow: a rate of transit of something which increases or decreases a Stock over time.
- Parameter: an element which represents a value, constant or computation, used in the model.
- Link: an element which communicates the value of one element of the model to one or more other elements of the model.
- Feedback: the communication of the result of an action back to the action itself. Feedback may be positive, adding to the action, or negative, subtracting from the action. It is feedback that is responsible for the emergent properties of models.
- Reinforcing Loop: a structure where reinforcing feedback causes the structure to exhibit growth as an emergent property.
- Balancing Loop: a structure where negative feedback causes the structure to exhibit balance as an emergent property.
- Emergent Properties: models have properties which cannot be found in any of the individual elements of the model though emerge from the interaction of the elements of the model.
- Boundary: Being aware of what's relevant to the model and what isn't forms a boundary for a model which is very important in helping to ensure the model doesn't become out of control.
- Systems Archetype: a structure which appears very frequently across all disciplines of science. The Reinforcing Loop and Balancing Loop are Systems Archetypes. There are additional System Archetypes which will be revealed in the next section.
[edit] Software
- The MapSys software is rich in function and easy to use. Take it one piece at a time.
- Build and test models little by little, and save multiple versions so if you run into a problem you can go back to the last working version. You'll become a believer in this one after you've added a dozen elements to a model and can't find which one is keeping it from working.
Wish you well continuing the journey.
[edit] References
- Simulation is not the Answer
- Sterman, John D. (1991) A Skeptic's Guide to Computer Models
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