Copyright,1995-2002

1

Invitation to Research

SYSTEMS THINKING

Roger Clarke, Xamax Consultancy, CanberraVisiting Professor, CSIS, Uni of Hong Kong

Visiting Fellow, Australian National University

http://www.anu.edu.au/people/Roger.Clarke/......Res /15-Sys.ppt

ebs, 16-20 January 2003

Copyright,1995-2002

2

Agenda

• Systems• Models• Cybernetics• Complexity of:

• System• Model• Behaviour

Copyright,1995-2002

3

A System• A set of interacting Real-World Entities• Interacts with its Environment across its Boundary• Entities within a System:

• gather inputs via Sensors• transmit outputs via Effectors• interact with one another via Interfaces

• Systems may:• exist at the same level (e.g. an mammal’s cardio-

vascular and digestive systems)• be related hierarchically (e.g. corpuscles within

blood within the cardio-vascular system)

Copyright,1995-2002

4

System Characteristics

• Degree of Closedness/Opennessto external Stimuli or Triggers

• EntropyThe tendency to lose energy and order

• NegentropyThe importation of energy to sustain order

• Unguidedness cf. Purposiveness• Adaptiveness/Learning

The ability to change as a result of stimuli

Copyright,1995-2002

5

A Model• An Abstract-World Representation

of a Real-World System• Iconic or Symbolic/Mathematical• Capable of being:

• viewed (e.g. a map• manipulated (e.g. a model aircraft in a

wind-tunnel)in ways that the System cannot be

• Necessarily (greatly) simplified• ‘The only reliable model of a real-world

system is the system itself’ (Pratchett)

Copyright,1995-2002

6

Categories of Models

• Deterministic Models – Automata• Computable by Analytical Methods• Too Complex to Compute, hence

Requiring Numerical Methods• Probabilistic Models• Non-Deterministic / Stochastic

Models• Entities exercising

Self-Determination / Free Wille.g. Humans and Organisations

Copyright,1995-2002

7

Simple Process Model

ProcessInputOutput

Copyright,1995-2002

8

Process Model with Controller

ProcessSensorsEffectorsControllerMeasuresInputOutputChanges

Copyright,1995-2002

9

Cybernetics• Control Loop:

• Inputs or Process Parameters changedas a result of measurement of Outputs

• Feedback:Positive / Reinforcing or Negative / Retardent

• Static Equilibrium / Steady-State cf.Dynamic Equilibrium / Homeostasis

• Delays, Control Limits, Tolerances=> Hunting / Hysteresis, Over-Correction

• Feedforward• Tiered Control Loops exhibit Complex Behaviour

Copyright,1995-2002

10

Levels of Discourse About Systems (Boulding)

• Framework Anatomy• Balanced Dynamic Clockwork• 1st-Order Control Thermostat• Open, Self-Maintaining Cell (in Biology)• Genetic-Societal Plant• Self-Aware, Purposive Animal (& Orgn?)• Self-Conscious Human• ...