Some systems are too large to be understood entirely by any one human mind. They are composed of a diverse array of individual components capable of interacting with each other and adapting to a changing environment. As systems, they produce behavior that differs in kind from the behavior of their components. Complexity Theory is an emerging discipline that seeks to describe such phenomena previously encountered in biology, sociology, economics, and other disciplines. Beyond new ways of looking at ant colonies, fashion trends, and national economies, complexity theory promises powerful insights to software development. The Internet—perhaps the most valuable piece of computing infrastructure of the present day—may fit the description of a complex system. Large corporate organizations in which developers are employed have complex characteristics. In this session, we'll explore what makes a complex system, what advantages complexity has to offer us, and how to harness these in the systems we build.

1. COMPLEXITY
THEORY SOFTWARE
DEVELOPMENT
and
@tlberglund
Wednesday, October 17, 12 1

2. Agents
Landscapes
Emergence
Complexity
Criticality
Connectedness
Wednesday, October 17, 12 2

3. Agents
Wednesday, October 17, 12 3

4. Agents are...
Simple
Interactive
Adaptive
Wednesday, October 17, 12 4

5. Why Does
TRAFFIC
Jam?
Wednesday, October 17, 12 5

6. Stuck
in TRAFFIC
Talking on cell
phone, not paying
attention...
I sure am in
all this
a hurry!
space! I'm'a
speed up.
Wednesday, October 17, 12 6

7. Stuck
TRAFFIC
in
maniAc!
Oh, my
bad.
@%$#%!
Wednesday, October 17, 12 7

8. Net
LOGO
http://ccl.northwestern.edu/netlogo/
Wednesday, October 17, 12 8

9. Net
LOGO
Wednesday, October 17, 12 9

10. Net
LOGO
Flocking
Alignment: a bird tends to move in the same
direction of nearby birds.
Separation: a bird will turn to avoid another bird
if they get too close.
Cohesion: a bird will tend to move towards other
nearby birds.
Wednesday, October 17, 12 10

11. Net
LOGO
Wednesday, October 17, 12 11

12. Agents
Landscapes
Emergence
Complexity
Criticality
Connectedness
Wednesday, October 17, 12 12

13. Landscapes
Wednesday, October 17, 12 13

14. Think of a
Problem
as a
SURFACE
Wednesday, October 17, 12 14

15. MT. FUJI
Wednesday, October 17, 12 15

16. Frederick
Winslow
TAYLOR
Wednesday, October 17, 12 16

17. RUGGED
LANDSCAPES
Wednesday, October 17, 12 17

18. Dancing
LANDSCAPES
Wednesday, October 17, 12 18

19. Agents
Landscapes
Emergence
Complexity
Criticality
Connectedness
Wednesday, October 17, 12 19

20. Criticality
Wednesday, October 17, 12 20

21. the Normal
DISTRIBUTION
Wednesday, October 17, 12 21

22. the Power Law
DISTRIBUTION
Wednesday, October 17, 12 22

23. Wednesday, October 17, 12
Rice PILES 23

24. Work
LOAD
Wednesday, October 17, 12 24

25. Work
LOAD
Wednesday, October 17, 12 25

26. Work
LOAD
Wednesday, October 17, 12 26

27. Work
LOAD
Wednesday, October 17, 12 27

28. Work
LOAD
Wednesday, October 17, 12 28

29. Work
LOAD
Wednesday, October 17, 12 29

30. Work
LOAD
Wednesday, October 17, 12 30

31. Work
LOAD
Wednesday, October 17, 12 31

32. Work
LOAD
Wednesday, October 17, 12 32

33. Work
LOAD
Wednesday, October 17, 12 33

34. Too much
Utilization leads to
CRITICALITY
Wednesday, October 17, 12 34

35. Agents
Landscapes
Emergence
Complexity
Criticality
Connectedness
Wednesday, October 17, 12 35

36. Connectedness
Wednesday, October 17, 12 36

37. A really basic refresher in
Graph
THEORY Seriously...BASIC.
Wednesday, October 17, 12 37

38. Degree 5
Degree 1
Degree 4
Wednesday, October 17, 12 38

39. To here
From here
Path Length= 3
Wednesday, October 17, 12 39

40. Network
FUNCTIONALITY
Wednesday, October 17, 12 40

41. Information
DIFFUSION depends on Path Length
Wednesday, October 17, 12 41

42. Robustness to
FAILURE depends on degree distribution
Wednesday, October 17, 12 42

43. Agents
Landscapes
Emergence
Complexity
Criticality
Connectedness
Wednesday, October 17, 12 43

44. Emergence
Wednesday, October 17, 12 44

45. Slime
Wednesday, October 17, 12
MOLD 45

46. Slime Mold Emergence
Wednesday, October 17, 12 46

47. Conway’s
Game
of
Wednesday, October 17, 12
LIFE 47

48. 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.
Wednesday, October 17, 12 48

49. Wednesday, October 17, 12 49

50. Wednesday, October 17, 12 50

51. Wednesday, October 17, 12 51

52. Surprise!
it’s a
COMPUTER
Wednesday, October 17, 12 52

53. Von Neumann
ARCHITECTURE
Wednesday, October 17, 12 53

54. Wednesday, October 17, 12 54

55. Wednesday, October 17, 12 55

56. Ant
COLONIES
Wednesday, October 17, 12 56

57. Wednesday, October 17, 12 57

58. Proceed with
CAUTION
Wednesday, October 17, 12 58

59. Software as a
COMPLEX
Profession
Wednesday, October 17, 12 59

60. AGENT-
BASED
DECISION
MAKING
Wednesday, October 17, 12 60

61. Wednesday, October 17, 12 61

62. What kind of
Software
Architecture would look like an
ANT
Wednesday, October 17, 12
COLONY? 62

63. Wednesday, October 17, 12 63

64. Wednesday, October 17, 12 64

65. Hypertext as the
Engine
of
APPLICATION
STATE
http://bit.ly/HATEOAS
Wednesday, October 17, 12 65

66. the way
HATEOAS
Works
GET /sandwich
Service
Web Service
Wednesday, October 17, 12 66

67. HATEOAS
the way
Works
Service
400 ERROR
<link rel=”bread” />
<link rel=”ingredient” />
Web Service
Wednesday, October 17, 12 67

68. HATEOAS
the way
Works
POST /sandwich
bread=rye
Service meat=pastrami
Web Service
Wednesday, October 17, 12 68

69. HATEOAS
the way
Works
Service
201 OK
<link href=”sandwich”>
<link href=”eat” />
<link href=”side” />
Web Service
Wednesday, October 17, 12 69

70. Make me a
Add Toppings
Sandwich I make Give me a
sandwiches.
sandwich, and I
can decorate it
with toppings.
I exchange
sandwiches
I toast Federal
for
sandwichReserve
buns.Notes.
Checkout
Toast Bun
Wednesday, October 17, 12 70

71. REST done
RIGHT
Wednesday, October 17, 12 71

72. Class
Are your
Dependencies
like a
RICE PILE?
Wednesday, October 17, 12 72

73. 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.
Wednesday, October 17, 12 73

74. remember the Power Law
DISTRIBUTION
Wednesday, October 17, 12 74

75. grails-web
900
675
450
225
0
Wednesday, October 17, 12 75

76. Hibernate 3
1500
1125
750
375
0
Wednesday, October 17, 12 76

77. Spring 3 Core
300
225
150
75
0
Wednesday, October 17, 12 77

78. toward a
COMPLEX
THEORY of
SOFTWARE
DEVELOPMENT
Wednesday, October 17, 12 78

79. Agents
Landscapes
Emergence
Complexity
Criticality
Connectedness
Wednesday, October 17, 12 79

80. Thank You
Tim Berglund
tlberglund@github.com
@tlberglund
Wednesday, October 17, 12 80

81. ACKNOWLEDGMENTS
http://bit.ly/unde
rstanding-compl
exity
Wednesday, October 17, 12 81

82. 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
Wednesday, October 17, 12 82