Complexity Theory and Software Development

COMPLEXITY
THEORY SOFTWARE
DEVELOPMENT
and

by Tim Berglund
Monday, June 21, 2010

ACKNOWLEDGMENTS


ACKNOWLEDGMENTS

http://bit.ly/unde
rstanding-compl
exity


ACKNOWLEDGMENTS

http://bit.ly/understanding-complexity

The Santa Fe Institute is a private, not-for-profit,
independent research and education center founded in 1984,
for multidisciplinary collaborations in the physical,
http://www.santafe.edu biological, computational, and social sciences.
Understanding of complex adaptive systems is critical to
addressing key environmental, technological, biological,
economic, and political challenges.

Renowned scientists and researchers come to Santa Fe
Institute from universities, government agencies, research
institutes, and private industry to collaborate in attempts to
uncover the mechanisms that underlie the deep simplicity
present in our complex world.


Agents
Landscapes
Emergence

Complexity

Criticality
Connectedness


Agents are...


Agents are...

Simple


Agents are...

Simple
Interactive


Agents are...

Simple
Interactive
Adaptive

Why Does

TRAFFIC
Jam?

Stuck
TRAFFIC
in


Stuck
in TRAFFIC

all this
space! I'm'a
speed up.


Stuck
TRAFFIC
in

Talking on cell
phone, not paying
attention...


Stuck
TRAFFIC
in

I sure am in
a hurry!


Stuck
TRAFFIC
in
maniAc!


Stuck
TRAFFIC
in

Oh, my
bad.


Stuck
TRAFFIC
in

@%$#%!


Gameof
Conway’s
LIFE


Gameof
Conway’s
LIFE
1. Any live cell with fewer than two live neighbors
dies.

2. Any live cell with more than three live neighbors
dies.

3. Any live cell with two or three live neighbors lives.

4. Any dead cell with exactly three live neighbors
comes to life.


Landscapes


Think of a

Problem
as a

SURFACE

MT. FUJI


Frederick
Winslow
TAYLOR


RUGGED
LANDSCAPES


Dancing
LANDSCAPES


What’s the

Quickest Way to the

SUMMIT?

EXPLORATION vs.

EXPLOITATION

Criticality


the Normal
DISTRIBUTION


the Central
LIMIT
Theorem


the Central
LIMIT
Theorem

“The mean value of a repeatedly
sampled random variable approaches a
normal distribution as the sample size
approaches infinity.”


the Central
LIMIT
Theorem

“The world is pretty much a normal place.”


the Power Law
DISTRIBUTION


Rice PILES

Work
LOAD


Too much

Optimization leads to

CRITICALITY

Connectedness


A really basic refresher in

Graph
THEORY

A really basic refresher in

Graph
THEORY Seriously...BASIC.


Degree 5


Degree 4


Degree 1


From here


To here

From here


To here

From here

Path Length= 3

CLUSTERING


SmallWORLDS


Network
FUNCTIONALITY


Information
DIFFUSION

Information
DIFFUSION depends on Path Length


Robustness to

FAILURE depends on degree distribution


Networks and

COMPLEXITY

NODES


AGENTS


Schools of

FISH

Schools of

FISH
Flocks of

BIRDS

Standing
OVATIONS

Standing
OVATIONS
Audience
PARTICIPATION

Emergence


Slime

MOLD

Slime Mold Emergence


Conway’s

Game
of

LIFE

Gameof
Conway’s
LIFE
1. Any live cell with fewer than two live neighbours
dies.

2. Any live cell with more than three live neighbours
dies.

3. Any live cell with two or three live neighbors lives.

4. Any dead cell with exactly three live neighbors
comes to life.


Surprise!
it’s a
COMPUTER


Von Neumann
ARCHITECTURE


Ant
COLONIES

Proceed with

CAUTION

Weak
EMERGENCE

Weak
EMERGENCE
Can’t predict it


Weak
EMERGENCE
Can’t predict it

CAN explain it after the fact


Strong
EMERGENCE

Strong
EMERGENCE
Can’t predict it


Strong
EMERGENCE
Can’t predict it

Can’t explain it after the fact either!


Strong
EMERGENCE
Can’t predict it


It’s just there, man


Strong
EMERGENCE
Can’t predict it


It’s just there, man

Deal with it

I said...

CAUTION

Software as a

COMPLEX
Profession

Lean says:


Lean says:

Optimize
the

WHOLE

Lean says:

Optimize
the

WHOLE
http://agilesoftwaredevelopment.com/blog/pbielicki/optimize-the-whole

Optimize

THIS!

“This is the constitutional limitation of

man's knowledge and interests, the fact

that he cannot know more than a tiny

part of the whole of society and that

therefore all that can enter into his

motives are the immediate effects which

his actions will have in the sphere he

knows.”

—F.A. Hayek

AGENT-
BASED
DECISION
MAKING


Software
Architecture


What kind of

Software
Architecture would look like an

ANT
COLONY?

SOAP
the way

Works


SOAP
the way

Works
Desktop App

Web Service

SOAP
the way

Works
Desktop App

<soap:Envelope>
make me a sandwich
</soap:Envelope>

Web Service

the way

<soap:Envelope>
SOAP
Works
FAIL
DELI009283
</soap:Envelope>
Desktop App

Web Service

SOAP
the way

Works
Desktop App

<soap:Envelope>
make me a pastrami
on rye?
</soap:Envelope>

Web Service

the way

<soap:Envelope>
SOAP
Works
FAIL
DELI276193
</soap:Envelope>
Desktop App

Web Service

Contracts are

Imposed
from the

TOP
DOWN

Hypertext as the

Engine
of

APPLICATION
STATE
http://bit.ly/HATEOAS


HATEOAS
the way

Works


HATEOAS
the way

Works
Service

Web Service

HATEOAS
the way

Works
Service

GET /sandwich

Web Service

the way
HATEOAS
Works
500 ERROR
<link rel=”bread” />
<link rel=”ingredient” />
Service

Web Service

HATEOAS
the way

Works
Service

POST /sandwich
bread=rye
meat=pastrami

Web Service

the way
HATEOAS
Works
200 OK
<link href=”eat” />
<link href=”side” />
Service <sandwich-body>...

Web Service

Make me a
Add Toppings
Sandwich

Checkout
Toast Bun


Make me a
Add Toppings
Sandwich I make
sandwiches.

Checkout
Toast Bun


Make me a
Add Toppings
Sandwich Give me a
sandwich, and I
can decorate it
with toppings.

Checkout
Toast Bun


Make me a
Add Toppings
Sandwich

I toast
sandwich
buns.

Checkout
Toast Bun


Make me a
Add Toppings
Sandwich

I exchange
sandwiches
for Federal
Reserve
Notes.

Checkout
Toast Bun


Behavior
Emerges
from the

EDGES
IN

Class
Are your

Dependencies
like a

RICE PILE?

Afferent
COUPLING
A class's afferent coupling is a measure of how many

other classes are coupled to it through method calls,

field accesses, inheritance, arguments, return

types, and exceptions.


remember the Power Law
DISTRIBUTION


grails-web
900

675

450

225

0


Hibernate 3
1500

1125

750

375

0


Spring 3 Core
300

225

150

75

0


having a


having a
Scale-Free
CODE BASE

toward a
COMPLEX
THEORY of

SOFTWARE
DEVELOPMENT

Thank You
Tim Berglund
www.augusttechgroup.com
tim.berglund@augusttechgroup.com
@tlberglund


Photo Credits
Slime Mold Cells
http://campus.queens.edu/faculty/jannr/Botany/images/slimies/slimeMolds/slimeMold1152.jpg

Car Top View
http://www.motiontrends.com/2006/m09/Volvo/C30.shtml

Ants
http://www.flickr.com/photos/binux/2495709841

Traffic Jam
http://www.flickr.com/photos/lynac/321100379/

Turning Machine
http://www.ecs.syr.edu/faculty/fawcett/handouts/webpages/CoreTechnologies.htm

VonNeumann Machine
http://en.wikipedia.org/wiki/File:Von_Neumann_architecture.svg

Ant Colony
http://www.bioone.org/doi/full/10.1672/1536-2442%282004%29004%5B0001%3ATNAOTF%5D2.0.CO%3B2

Mt. Fuji
http://www.flickr.com/photos/mtsn/229410448

Snowy Mountains
http://www.flickr.com/photos/huzhead/85362599

Portrait of Frederick Winslow Taylor
http://upload.wikimedia.org/wikipedia/commons/9/90/Frederick_Winslow_Taylor_crop.jpg

Female Velvet Ant (in Work Load Illustration)
http://www.flickr.com/photos/markop/1036891509

Frederick Hayek
http://www.lancs.ac.uk/staff/ecagrs/Hayek%20quotes.htm


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