Poietic Flows

Systems Dynamics Modelling and simulation toolkit based on the Stock and Flow methodology.

Core functionality:

• Creation and iterative design of stock and flow models.
• Simulation of systems dynamics models.

Features

Current:

• Stock and Flow model
  • Nodes: Stock, Flow, Auxiliary, Graphical Function
  • Interface nodes: Chart, Control
  • Included Euler and RK4 solvers
  • Experimental features: Delay
• Simple arithmetic expressions (formulas)
  • Built-in functions: abs, floor, ceiling, round, power, sum, min, max
• Whole editing history is preserved.
• Editing is non-destructive and can be reversed using undo and redo commands.
• Exports:
  • Graphviz dot files.
  • Export to CSV.
  • Charts to Gnuplot

See also: PoieticCore.

Planned:

• More useful built-in functions and variables for the Stock and Flow model.
• Sub-systems.

Installation

Available platforms: MacOS 14 (and later), Linux

To install the poietic command-line tool, run the following command in the project's top-level directory:

./install

The tool will be installed in the Swift Package Manager's' ~/.swiftpm/bin directory. Make sure you have the directory in your PATH, if you do not, then add the following to the end of your ~/.zshrc or ~/.bashrc file:

export PATH=~/.swiftpm/bin:$PATH

Examples

The examples are located in the Examples repository. Follow instructions how to run them in the documentation contained within the repository.

Documentation

• Stock and Flow package: PoieticFlows
• Object Graph modelling package: PoieticCore

Tool

The Poietic Flows includes a command-line tool to create, edit and run Stock and Flow models called poietic.

See the Command Line Tool documentation.

Command summary:

• new: Create an empty design.
• info: Get information about the design
• list: List design content objects.
• show: Describe an object.
• edit: Edit an object or a selection of objects.
  • set: Set an attribute value
  • undo: Undo last change
  • redo: Redo undone change
  • add: Create a new node
  • connect: Create a new connection (edge) between two nodes
  • remove: Remove an object – a node or a connection
  • auto-parameters: Automatically connect parameter nodes: connect required, disconnect unused
  • layout: Lay out objects
  • align: Align objects on canvas
• import: Import a frame into the design.
• run: Run the simulation and generate output
• write-dot: Write a Graphviz DOT file.
• metamodel: Show the metamodel
• create-library Create a library of multiple models.

Use --help with a desired command to learn more.

Pseudo-REPL

Think of this tool as ed but for data represented as a graph. At least for now.

The tool is designed in a way that it is by itself interactive for a single-user. For interactivity in a shell, set the POIETIC_DATABASE environment variable to point to a file where the design is stored.

Example session:

poietic new
poietic info

poietic edit add Stock name=water formula=100
poietic edit add Flow name=outflow formula=10
poietic edit connect Drains water outflow

poietic list formulas

poietic edit add Stock name=unwanted formula=0
poietic list formulas
poietic edit undo

poietic list formulas

poietic run

Author

Stefan Urbanek