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EMER: Introduction

EMER is taught by

Susan Stepney

and Fiona Polack

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Module Structure

1, 2 Introduction; Some definitions of emergence Fiona

3, 4 Cellular Automata and related systems Susan

5 Variants on cellular automata Susan

6 L-systems Susan

7, 8 Examples of emergence in natural systems Fiona

9, 10

Information theory: Defining and measuring complexity

Susan

11, 12

Comparing measures and uses of complexity Susan

13 Information theoretic views of emergence and self-organisation

Fiona

14-16

Engineering of emergence and engineering for emergence

Fiona

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But first …some introductory ideas

• Emergence Behaviour observed at one scale is not apparent

at other scales

• Self-organisation Structures that emerge without systematic

external stimuli

• Complexity On a continuum between totally ordered and

totally random

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Emergence

At the low level (here molecular or nano-scale): particles do their thing

What is this?

Could be pretty much anything!

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Emergence

Particles are water molecules – emergent effect is flowing water

Behaviour is observable at a higher level – macro-scale

Wharfe, Burnsall, March 2006

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Emergence

Actual effects observed depend on things in the environment: riverbed depth (volume of water) gradient, etc.

Moselle, June 2006

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Emergence

Troller’s Gill,, March 2006

But there is minimal variation among particles

Also, a few million fewer particles makes little difference to what is observed

… and a few billion billion fewer just gives a slightly shallower river

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• Science and engineering interest:

• An emergent system is a system of systems Emergent properties at system level Components at system level

• Emergence cannot be understood by looking either at the composed system or the component systems

Why study emergence

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How will we study emergent systems?

• Simulation examples Components with simple rules – L-systems, CAs …

[Prusinkiewicz & Lindenmeyer, fig 1.24a, c, d, 1.10, 1.24f, 1.8]

Gosper’s CA glider gun :

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How will we study emergent systems?

• Natural examplesBuilding – social insects

http://iridia.ulb.ac.be/~mdorigo/ACO/RealAnts.html

Networks – ants

Flocking – birds and fish http://www.fotosearch.com/PDS136/200351304-001/

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How is emergence recognised?

1. Observation or description

Cannot describe using the same terminology for component and emergent behaviours1

• e.g. Game of Life CA glider: components are static coloured cells but glider is a moving block of one colour

• e.g. Pile of sand grains: size, mass, of pile are sum of grain values, but slope of pile emerges from combined behaviours of grains

1 But see Smith and Sanders’ work on formally demonstrating the link across levels: e.g. Jeff W. Sanders, Graeme Smith: Emergence and refinement. Formal Asp. Comput. 24(1): 45-65 (2012)

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How is emergence recognised?

2. Measurement (to some approximation)

Information theoretic models of emergence Entropy and how it changes at different

scales Postulated edge-of-chaos and its link to

emergent behaviour Distinguishing emergent characteristics or

types Clarifying similar concepts

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Where might study of emergence lead?

1. Engineering emergent systems Realising Drexler’s vision of molecular

nanotechnology used for constructing and repair Nano-scale construction is already viable

Molecular nanotech. simulations are well developed

Some form of engineered complex emergent systems exist at the macro-scale Human organisations, networking etc.

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Where might study of emergence lead?

2. Simulation Scientific research into complex systems is

difficult Observation perturbs the system “live” systems may be unobservable at the

level needed Computer simulation may offer an alternative

Platform for developing and exploring hypotheses

Simulations must be developed and used in ways that support accurate interpretation of results

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How can an emergent system be engineered?

In so far as we can answer this at all …

•Understand what emergence means studying lots of emergent systems

•Consider appropriate levels and views of system and its environment

•Work out how simulation can contribute What needs to be modelled What it tells us about reality

•Pay attention to assurance needs