In order to show how parametric computer modeling can be related to Meadows’ Thinking in Systems text, I propose some preliminary grasshopper explorations.
FILLING UP A BATHTUB.
A simple definition showing the rate of change in the volume (stock) of a bathtub as it is filled at a constant rate:
A definition showing what happens when the rate of change is multiplied by a fraction less than 1:
as the fraction size increases, the volume increases at a greater rate of change, implying that the rate of inflow has sped up.
Notes: the flow definitions in Grasshopper are different than Meadows’ diagrams in a number of ways. For example, Grasshopper definitions tend to begin with whatever function determines the overall condition of the system and end with the resulting “stock” as a model. In contrast, Meadows’ diagrams seem to flow from left to right on a generally time-based scale. Also, Grasshopper allows for two specific modes of visualizing these relationships: through the flow definition that shows direct connections and relationships between system components, and through a 3 dimensional model of the resulting stock.
One of the similarities between the two system outlines is that they have the capacity to self-reference, opening the possibility of expressing different kinds of systems (positive feedback, self balancing, etc.)
Conclusion: Grasshopper provides a lens for visualizing specific, logic based relationships within systems.