Course Introduction
and Overview
Networked Life
CSE 112
Spring 2006
Prof. Michael Kearns
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Internet, Router Level
A purely technological network?
“Points” are physical machines
“Links” are physical wires
Interaction is electronic
What more is there to say?
• Points: power stations
• Operated by companies
• Connections embody
business relationships
• Food for thought:
– 2003 Northeast blackout
North American Power Grid
• Points are still machines… but
are associated with people
• Links are still physical… but
may depend on preferences
• Interaction: content exchange
• Food for thought:
“free riding”
Gnutella Peers
• Points: sovereign nations
• Links: exchange volume
• A purely virtual network
Foreign Exchange
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Purely biological network
Links are physical
Interaction is electrical
Food for thought:
– Do neurons cooperate or compete?
The Human Brain
The Premise of Networked Life
• It makes sense to study these diverse networks together.
• The Commonalities:
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Formation (distributed, bottom-up, “organic”,…)
Structure (individuals, groups, overall connectivity, robustness…)
Decentralization (control, administration, protection,…)
Strategic Behavior (economic, free riding, Tragedies of the Common)
• An Emerging Science:
– Examining apparent similarities between many human and technological
systems & organizations
– Importance of network effects in such systems
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How things are connected matters greatly
Details of interaction matter greatly
The metaphor of viral spread
Dynamics of economic and strategic interaction
– Qualitative and quantitative; can be very subtle
– A revolution of measurement, theory, and breadth of vision
Who’s Doing All This?
• Computer Scientists
– Understand and design complex, distributed networks
– View “competitive” decentralized systems as economies
• Social Scientists, Behavioral Psychologists, Economists
– Understand human behavior in “simple” settings
– Revised views of economic rationality in humans
– Theories and measurement of social networks
• Physicists and Mathematicians
– Interest and methods in complex systems
– Theories of macroscopic behavior (phase transitions)
• All parties are interacting and collaborating
Course Mission
• A network-centric examination of a wide range of social,
technological, biological, financial and political systems
• Examined via the tools and metaphors of:
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computer science
economics
psychology and sociology
mathematics
physics
• Emphasize the common themes
• Develop a new way of examining the world
A Communal Experiment
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No similar undergraduate course
No formal technical prerequisites
– greatly aided by recent books
– publications in Science, Nature, etc.
– preliminary class demographics:
• ~37% freshmen/sophomore
• ~52% College/Wharton
Extensive web visualizations and demos
Extensive participatory in-class and out-of-class social experiments
Exercises in data analysis
Note: Networked Life is now approved to fulfill the College’s
Quantitative Data Analysis Requirement
Also counts as an SEAS engineering elective course
Course Outline
The Networked Nature of Society
(~2 lectures)
• Networks as a collection of pairwise relations
• Examples of (un)familiar and important networks
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social networks
content networks
technological networks
biological networks
economic networks
• The distinction between structure and dynamics
A network-centric overview of modern society.
Contagion, Tipping and Networks
(~2 lectures)
• Epidemic as metaphor
• The three laws of Gladwell:
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– Law of the Few (connectors in a network)
– Stickiness (power of the message)
– Power of Context
The importance of psychology
Perceptions of others
Interdependence and tipping
Paul Revere, Sesame Street, Broken Windows, the
Appeal of Smoking, and Suicide Epidemics
Informal case studies from social behavior and pop culture.
Introduction to Graph Theory
(~1 lecture)
• Networks of vertices and edges
• Graph properties:
– cliques, independent sets, connected components, cuts,
spanning trees,…
– social interpretations and significance
• Special graphs:
– bipartite, planar, weighted, directed, regular,…
• Computational issues at a high level
Beginning to quantify our ideas about networks.
Social Network Theory
(~3 lectures)
• Metrics of social importance in a network:
– degree, closeness, between-ness, clustering…
• Local and long-distance connections
• SNT “universals”
– small diameter
– clustering
– heavy-tailed distributions
• Models of network formation
– random graph models
– preferential attachment
– affiliation networks
• Examples from society, technology and fantasy
A statistical application of graph theory to human organization.
The Web as Network
(~2 lectures)
• Empirical web structure and components
• Web and blog communities
• Web search:
– hubs and authorities
– the PageRank algorithm
• The Main Streets and “dark alleys” of the web
The algorithmic implications of network structure.
Towards Rationality:
Emergence of Global from Local
(~1 lecture)
• Beyond the dynamics of transmission
• Context, motivation and influence
• The madness/wisdom of crowds:
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thresholds and cascades
mathematical models of tipping
the market for lemons
private preferences and global segregation
Begin to connect to classical issues
of human and societal behavior.
An Introduction to Game Theory
(~2 lectures)
• Models of economic and strategic interaction
• Notions of equilibrium
– Nash, correlated, cooperative, market, bargaining
• Multi-player games
• Evolutionary game theory
– mimicking vs. optimizing
• Network effects
• Social choice theory
Powerful mathematical models of what happens
over links in competitive and cooperative settings.
Interdependent Security and Networks
(~1 lecture)
• Security investment and Tragedies of the Commons
• Catastrophic events: you can only die once
• Fire detectors, airline security, Arthur Anderson,…
Blending network, behavior and dynamics.
Network Economics
(~2 lectures)
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Buying and selling on a network
Modeling constraints on trading partners
Local imbalances of supply and demand
Preferential attachment, price variation, and the distribution of wealth
The effects of network structure on economic outcomes.
Behavioral Economics
(~1 lectures)
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What’s broken with economics and game theory?
How should you split 20 dollars?
Beauty contests and ultimatums
Cultural and sociological effects
The return of context
Guilt, envy and altruism: improving the theory
Controlled social psychology experiments
examining how “rational” we really are(n’t).
Internet Basics
(~1 lecture)
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IP addresses
Routers
Domain Name Servers
ISPs
Congestion control, load balancing
The Web and URLs
Security issues, network vulnerability
Under the hood of the quintessential
modern technological network.
Internet Economics
(~2 lectures)
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Selfish routing
The Price of Anarchy
Peer-to-peer as competitive economy
Paris Metro Pricing for QoS
Economic views of network security
The collision of network, economics,
algorithms, content, and society.
Modern Financial Markets
(~2 lectures)
• Stock market networks
– correlation of returns
• Market microstructure
– limit and market orders
– order books and electronic crossing networks
– network, connectivity and data issues
• Quantitative trading
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– VWAP trading, market making
– limit order power laws
Herd behavior in trading
Economic theory and financial markets
Behavioral economics and finance
Impacts of the Internet on financial markets
A study of the network that runs the world.
Course Mechanics
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Will make heavy use of course web page:
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No technical prerequisites!!!
Lectures:
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No recitations
Readings: mixture of general audience writings and articles from
the scientific literature
Three required texts:
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Assignments (~1/4 of grade)
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Participatory social experiments (~1/4 of grade)
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Midterm (~1/4 of grade)
Final exam (~1/4 of grade)
– www.cis.upenn.edu/~mkearns/teaching/NetworkedLife
– You will need good Internet access!
– slides provided; emphasis on concepts
– frequent demos, visualizations, and in-class experiments
– please be on time to lectures! (12PM)
– “The Tipping Point”, Gladwell
– “Six Degrees”, Watts
– “Micromotives and Macrobehavior”, Schelling
– data analysis: network construction project
– computer/web exercises, short essays, quantitative problems
– collaboration is not permitted
– behavioral economics experiments
– analysis of experimental results
First Assignment
• Due next lecture (Th 1/12)
– Simple background questionnaire
– Last-names exercise