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In this module we'll investigate a project environment where the amount of work completed each week is essentially determined by the amount of work that is remaining.

Contents 1 Create the Model 2 Simulate the Model 3 Observations and Insights 4 Reference

[edit] Create the Model

Use the modeling tools and create a model that looks like Fig. 1.

Define the following:

• Simulation Specs
  • starttime = 0
  • stoptime = 10 (10 weeks)
  • dt = 1
  • Integration Method = Euler's Method
• completed project = 0
• project completion = 10
• pct comp per week = 0.2 (20% of remaining project completed each week)
• work on project = (project_completion - completed_project) * pct_comp_per_week

[edit] Simulate the Model

Use the Graph Element and place a graph area in the work area then Double-Click on the graph area to open the Graph Editor. Click the Variables tab and add project completion, completed project and work on project to the graph. Now go back to the Chart tab and Right-Click on each of the plot scales, select properties and set Minium: = 0, and Maximum: = 11. With all the scales the same it's easier to see the comparison on the resultant graph.

Now Run the model and you should get a display that looks like Fig. 2.

You should notice that as the pct comp per week is increased the project nears completion sooner, which is as expected. What should be interesting though is the shape of the curve itself. As the project gets nearer and nearer to completion it moves toward completion more and more slowly, something you've probably painfully experienced already.

The structure itself is attempting to create a balance between completed project and project completion, yet the amount of work on project applied gets smaller and smaller. This structure is referred to as a Balancing Loop and behaves this way because the connection from completed project to work on project represents negative feedback.

[edit] Observations and Insights

• Balance: the Project Completion model exhibits a property of balance. As none of the individual elements of the model exhibit a property of balance this must be an Emergent Property, as Growth was an emergent property in the Savings Account model.
• Negative Feedback: The reason for balance is the connection between Completed Project and work on project. This connection represents what's referred to as negative feedback. Any time an action produces a result which encourages less of the same action you have negative feedback.
• Balancing Loop: The Project Completion structure is referred to as a Balancing Loop, specifically because it exhibits the Emergent Property of balance.
• System Archetype: The Balancing Loop is also referred to as a System Archetype. The reason is that the Balancing Loop is a structure that occurs very frequently across all disciplines of science.

Prev: Savings Account Continued * Next: Summary

[edit] Reference

• Diagrams created with MapSys

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