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.

Current:

• Stock and Flow model
  • Implemented nodes: Stock, Flow, Auxiliary, Graphical Function
  • Stocks can be either non-negative or can allow negative values
  • Included Euler and RK4 solvers
• 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.

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

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

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

At the moment, the only user-facing interface is a command-line tool called poietic. The available commands are:

  new                     Create an empty design.
  info                    Get information about the design
  list                    List all nodes and edges
  describe                Describe an object
  edit                    Edit an object or a selection of objects
  import                  Import a frame bundle into the design
  run                     Run a model
  write-dot               Write a Graphviz DOT file.
  metamodel               Show the metamodel

The edit subcommands are:

  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

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

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:

export POIETIC_DATABASE="MyDesign.poietic"

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
poietic list formulas
poietic edit undo

poietic list formulas

poietic run

Stefan Urbanek