Has anyone made Systems Dynamics abstractions for Pure Data?

Wikipedia has a good article on Systems dynamics: https://en.wikipedia.org/wiki/System_dynamics

I would like to create a simple "stock and flow" modeling environment. Stock and flow models can be as simple as predator/prey population fluctuation to global warming models following the carbon cycle. Such models are great education experiences, playing what if experiments, and the output could be charted in a table or used to drive a sonification or visualization of the model.

It seems almost trivial, stocks are accumulators (up or down) and flows are controlled by valves (multiplier), and a clock to step the model.

Thanks, Jeff Sandys