Pedro Ribeiro de Andrade Münster, 2013 Systems Theory Pedro Ribeiro de Andrade Münster, 2013

Systems Theory Provides a unified classification for scientific knowledge. Enunciated by biologist Ludwig Von Bertalanffy: 1920s: earliest developments 1937: Charles Morris Philosophy Seminar, University of Chicago 1950: “An Outline of General Systems Theory”, Journal for the Philosophy of Science Scientists that introduced Systems Theory in their fields: Parsons, sociologist (1951) J.G Miller, psychiatrist & psychologist (1955) Boulding, economist (1956) Rapoport, mathematician (1956) Ashby, bacteriologist (1958)

Conception of Reality Any measurable part of reality can be modeled Systems are represented as stocks and flows Stocks represent energy, matter, or information Flows connect and transport stocks Systems are opened or closed

A system Can you identify parts? and Do the parts affect each other? and Do the parts together produce an effect that is different from the effect of each part on its own? and perhaps Does the effect, the behavior over time, persist in a variety of circumstances? Source: (Meadows, 2008)

Earth as a system

Tools for system dynamics Dinamo Vensim Simile STELLA

Water in the tub Initial stock: water in tub = 40 gallons water in tub(t) = water in tub(t – dt) – outflow x dt t = minutes dt = 1 minute Runtime = 8 minutes Outflow = 5 gal/min

Cell (description extracted from “TerraME types and functions”) Not yet (description extracted from “TerraME types and functions”)

Event Not yet Not yet

Temporal model . . . false true Source: (Carneiro et al., 2013) 1:32:10 ag1:execute( ) 1:38:07 ag2:execute( ) 1:42:00 cs:save() . . . (4) ACTION return value true (1) Get first EVENT 1:32:00 cs:load( ) (2) Update current time (3) Execute the ACTION false (5) Schedule EVENT again Source: (Carneiro et al., 2013) 12

Observer Not yet

Water in the tub Initial stock: water in tub = 40 gallons water in tub(t) = water in tub(t – dt) – outflow x dt t = minutes dt = 1 minute Runtime = 8 minutes Outflow = 5 gal/min

Water in the tub 2 Initial stock: water in tub = 40 gallons water in tub(t) = water in tub(t – dt) – outflow x dt t = minutes dt = 1 minute Runtime = 8 minutes Outflow = 5 gal/min Inflow = 40 gal every 10 min

Conclusions Two ways to increase stocks Stocks act as delays or buffers Stocks allow inflows and outflows to be decoupled