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Sharing Mart: An Experimental Platform for Socio-Technological Networks Research

Dr. Hazer Inaltekin

Department of Electrical Engineering

Princeton University

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Agenda Today

Introduction and Motivation

Quick Introduction to the Sharing Mart System

Multi-unit Sharing Mart Auctions

Sharing Mart Experiments

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Introduction and Motivation Time

Sociology

Math

Physics

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Physics

Math

Physics

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Sociology Sociology

1950 1998

Milgram Granovetter

2006 Present

Watts Barabasi Kleinberg

Lots of funding (NSF, DARPA, ARMY) on

human-network interactions and joint socio-technological

network characterization !!!

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Introduction and Motivation Two Modes of Connections:

Physical connections via communication networks, virtual connections via social networks.

Human Factor in Play: Needs of people, virtual ties among them, how they use communication nodes.

P2P + Social Networks: More than 60% of total data traffic in Internet. Facebook: A Web Based Social Network.

More than 150 million active users, has an average 250K registrants per day since January 2007, has an average weekly growth rate around 3%.

Social Overlay - Communication Underlay Networks

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Introduction and Motivation An exponential increase in the number of social networking sites. An exponential increase in the number of active members.

Bottom line: Understand human behavior and social ties among people better design next generation communication networks.

18.2

66.8

38.3

0

10

20

30

40

50

60

70

80

2004 2005 2006 2007

Number ofUniqueMembers ofMySpace

Years

Mill

ions

Social Overlay - Communication Underlay Networks

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Introduction and MotivationSocial Overlay - Communication Underlay

Networks

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Vision and Motivation

Examples: Distributed decision making, trust formation, traffic engineering, network capacity and network connectivity

calculations, network resource allocation, wireless social networking.

Collaborators: Prof. Matthew Salganik from Sociology

Department at Princeton University. Prof. Jacob Shapiro from Political Science

Department at Princeton University/ Prof. Junshan Zhang from Electrical Engineering

Department at Arizona State University.

Social Overlay - Communication Underlay Networks

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Time/Resources v.s. Research Task

Trade-off

Tim

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Mathematical Modeling / Analysis

Agent Based Simulation and Empirical Data

Analysis

Testbed Design and Empirical Data

Collection / Analysis

1-) Topology of Socio-technological Networks and Delay Characterization

1-) Delay Simulations

2-) Yahoo Communication Network Data. (500 Gbyte)

1-) Sharing Mart Project

Introduction and Motivation

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Agenda Today

Introduction and Motivation

Quick Introduction to the Sharing Mart System

Multi-unit Sharing Mart Auctions

Sharing Mart Experiments

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Quick Introduction to Sharing Mart Sharing Mart, S-Mart, is a virtual money (token) based social file sharing platform for

Web users to come together and exchange their files. Innovative research agenda with fun functional modules. Current Status:

Active with 250 students in SEAS.

User Behavior Characterization

File Transactions Fixed Price or S-mart

Auction

Group Formation

Content RequestContent and User

Rating

User Generated Advertisements

Digital Rights Management

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Quick Introduction to Sharing MartSharing Mart System

http://sharingmart.princeton.edu

S-Mart Main Web Page Student Interests at SEAS

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Quick Introduction to Sharing MartPersonalized Home Pages

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Quick Introduction to Sharing MartPersonalized Web Stores

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Quick Introduction to Sharing MartContent Upload

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Quick Introduction to Sharing MartAd Upload

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Quick Introduction to Sharing MartContent Request

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Quick Introduction to Sharing MartGroup Formation

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Agenda Today

Introduction and Motivation

Quick Overview of the Sharing Mart System

Multi-unit Sharing Mart Auctions

Sharing Mart Experiments

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Multi-unit Sharing Mart Auctions

Auctions: A simple solution used since 500 B.C. to discover market value of goods.

Auctions

Single Unit Multi-unit

First Price Second Price

Ascending Price English Auctions

Descending Price Dutch Auctions

Vickery Auctions

Ebay Auctions

Discriminatory Uniform Vickery

Sharing Mart Auctions

Multi-unit Descending Price Dutch Auction

Ausubel Auctions

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Multi-unit Sharing Mart Auctions Sharing Mart Auction: is a uniform price, unit demand and multiple

winner file auction. Parameters: Auction duration, minimum price, number of copies to be

sold K. Can be specific to groups.

Market Clearing Price in Sharing Mart Auctions: (K+1)st highest bid. Definition: An auction is efficient if it allocates the goods to highest

bidders. Definition: An auction is incentive compatible if it induces a bidder to

submit a bid that sincerely reflects her value for the item. Revenue Equivalence: A Sharing Mart auction is revenue equivalent

to other two auction types (discriminatory and Vickery multi-unit

auctions).

Some Properties

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Multi-unit Sharing Mart AuctionsAuction Interface

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Agenda Today

Introduction and Motivation

Quick Overview of the Sharing Mart System

Multi-unit Sharing Mart Auctions

Sharing Mart Experiments

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Sharing Mart Experiments

Number of Participants: 19 undergraduate students. Number of Auctions: 4 Bidding Behavior:

Manual bidding Bidding strategy can change over time No restriction

Open Economy: Initial budget: 500 [Tokens] Can change over time by selling files and inviting friends in

SEAS to buy their files Close to collecting plain data in eBay

Experiment 1 - General Set-up

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Sharing Mart Experiments

Auction Parameters: Number of students = 19 Minimum price = 20 [Tokens] Number of copies = 2 Start Date: 11/1/2008 11:30:00 AM End Date: 11/4/2008 11:59:00 PM Duration: 304,140 [Seconds]

Auction Results: Final Price: 612 [Tokens] Number of unique bidders: 10 Total Income: 1224 [Tokens]

Experiment 1 - Auction 1 Set-up

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Sharing Mart Experiments

65

65

69

62, bids 612. Token balance 612

626959

Experiment 1 - Auction 1 Results

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Sharing Mart ExperimentsExperiment 1 - Auction 1 Results

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Sharing Mart Experiments

6965

62 - Token balance 612

55

Winners

Experiment 1 - Auction 1 Budget Distribution

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Sharing Mart Experiments

Auction Parameters: Number of students = 19 Minimum price = 20 [Tokens] Number of copies = 5 Start Date: 11/5/2008 2:00:00 AM End Date: 11/8/2008 11:59:00 PM Duration: 338,340 [Seconds]

Auction Results: Final Price: 551 [Tokens] Number of unique bidders: 14 Total Income: 2755 [Tokens]

Experiment 1 - Auction 2 Set-up

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Sharing Mart Experiments

5455

60 bid amount = 707

60 bid amount = 710

59

57

37

62, bids 616. Token balance

616

Experiment 1 - Auction 2 Results

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Sharing Mart ExperimentsExperiment 1 - Auction 2 Results

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Sharing Mart Experiments

55 65 69

They do not bid

60, token balance = 710

57, 59

But they are not winners

They are among winners

37, 62, 54

They are among winners

Experiment 1 - Auction 2 Budget Distribution

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Sharing Mart Experiments

Auction 3: Number of copies = 7 Total Income: 3500 [Tokens]

Auction 4: Number of copies = 9 Total Income: 180 [Tokens]

Experiment 1 - Auction 3 and 4

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Sharing Mart ExperimentsSeller Revenue Optimization

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Sharing Mart Experiments

ELE 382

SEAS

Intra-community Links

Inter-community Links

Community Structure

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Sharing Mart Experiments

Number of Participants: 7 graduate students. Bidding Behavior:

Automated bidding. Bidding strategy does not change over time.

Closed Economy: Initial budget: 1800 [Tokens]. Can change over time by selling/buying files from other 6 graduate students.

96-hours Auction Competition: Each student sets 3 auctions to sell - Seller Strategy:

Free Parameters: Number of items, duration and minimum price. Each student submits an automated bidding agent to bid 18 auctions - Buyer Strategy.

Total Number of Points Collected: Number of Auctions Won * 100 + Total Revenue in 3 Auctions.

Experiment 2 collects auction data in a controlled manner.

Experiment 2 - General Set-up

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Sharing Mart ExperimentsExperiment 2 - General Set-up

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Sharing Mart Experiments

Points of Student i: is the number of items sold in auction k from student i. is the final sale price in auction k from student i. is equal to 1 if student i wins auction k from student j.

Score Function to Optimize:

Experiment 2 - Nash Equilibrium

: Minimum sale price in auction k from student i

: Duration of auction k from student i

: Bidding strategy of student j

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Sharing Mart Experiments

Theorem: The above experiment has a symmetric and socially optimal Nash equilibrium at which:

Note: At this equilibrium, all students earn 3600 points, therefore a score of 100.

Experiment 2 - Nash Equilibrium

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Sharing Mart Experiments

Average Number of Copies (Averaged over 3 Best Seller Strategies) is 5.33.

Nash equilibrium predicts this number to be 6.

Experiment 2 Results - Revenue v.s. Number of Copies

All students benefit from setting number

of copies to 6.

Conclusion 1

Average revenue increase is 20%.

Conclusion 2

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Sharing Mart ExperimentsExperiment 2 Results - Revenue v.s. Number of

Copies

Minimum Price = 97

Empirical revenue versus number of copies curve

peaks around 5-6 copies.

Conclusion 3

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Sharing Mart Experiments

Minimum Price: Average minimum price over all auctions is 97 [Tokens]. Average minimum price over three best sellers is 95 [Tokens]. High minimum price decreases the percentage of copies sold.

All copies are sold if the minimum price is below 80 but none of the all copies sold if

minimum price is above 100. Conclusion 4: Nash equilibrium strategy minimum price matches with the

empirically observed minimum price.

Bidding Strategy: Three most successful bidders with success rate 97% snipe within the last 60

seconds. Average number of bids per auction from the three most successful bidders is 1.3. Continuous bidding with 8.6 bids per auction reduces to the success rate to 62%. Conclusion 5: Small average number of bids per auction is in accordance with the

efficiency and incentive compatibility property of Sharing Mart auctions.

Experiment 2 Results - Effects of Other Parameters

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Summary and Conclusions

Boundaries between sociology, physics, computer science and electrical engineering are disappearing.

New Networking Paradigm: Social Overlay - Communication Underlay

Sharing Mart: Collect data in