emer: introduction
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EMER: Introduction. EMER is taught by Susan Stepney and Fiona Polack. Module Structure. 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 - PowerPoint PPT PresentationTRANSCRIPT
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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