Presentation :Finding a Team of Experts in Social Networks

Jack Cheng Ka HoThe Chinese University of Hong

Kong

SEEM 5010Advanced Database and Information System

Motivation•A pool of individuals with different skills

+ A social network ▫Finding a subset

•TEAM FORMATION Problem

•Not only meet Skill Requirements•Can also work Effectively Together as a

teamHow can I find a team of experts that can collaborate

effectively in order to complete a given task?

Problem•Given a Task and a set of Experts in

Network▫Goal: find a set of individuals that can

effectively perform the task

•Task(T): Set of required skills

•Expert(X): Individual with specific skill-set

•Network(G): Strength of Relationships▫Weights on the edges = Communication

Cost

Expertise Networks•Companies (Organizational Structure):

▫Same group or department Easily Communicate

•Research Community:▫Collaboration Networks

•Other examples of Social Networks▫LinkedIn, Xing and others

How to make a team effective for a given task?•T = {algorithms, software engineering,

distributed systems, web programming}

•Without considering the social network…▫Result: X’ = {A,B,C}

▫Result: X” = {A,E}

A{algorithm

s}

B{web

programming}

D{software engineerin

g}

C{software

engineering, distributed systems}

E{software

engineering, distributed systems, web programming}

A{algorithm

s}

B{web

programming}

C{software

engineering, distributed systems}

E{software

engineering, distributed systems, web programming}

A{algorithm

s}

How to make a team effective for a given task?•With the social network …

•TEAM FORMATION with considering a Social Network▫Coverage + Communication

T={algorithms, software engineering, distributed systems, web programming}

D{software engineerin

g}

B{web

programming}

C{software

engineering, distributed systems}

E{software

engineering, distributed systems, web programming}

A{algorithm

s}

A

B C

D

E

A, B and C form an effective

group to communicate

A and E could perform task if

they could communicate

Problem Definition•Given

▫The set of n individuals X={1,…,n}▫Graph G(X,E) ▫Task T

•Find X’▫With C(X’,T)=T :▫And Communication Cost Cc(X’) is

minimized

•Good Teams▫Have all necessary skills▫Can communicate effectively

X’ have the necessary

skills

E= Edge

How to measure effective communication?•Diameter (R)

▫The largest shortest path between any two node in the subgraph

▫Diameter Communication Cost of X’ Cc-R(X’)

A

B C E

DA

ECB

diameter = inftydiameter = 1

How to measure effective communication?•Minimum Spanning Tree (MST)

▫The sum of the weights of its edge that spans all the team nodes

▫MST communication cost Cc-MST(X’)

A

B C E

DA

ECB

MST = inftyMST = 2

Diameter-TEAM FORMATION problem

A B

C

E

D

T={algorithms,java,graphics,PHP}

{graphics,PHP,java}

{algorithms,graphics}

{algorithms,graphics,java}

{PHP}

αrare= algorithmsSrare={B, E}

B

E

A Skills: algorithmsgraphicsjavaPHP

Diameter = 2αrare= javaSrare={A, C, E}αrare= PHPSrare={A,C,D}

{PHP,java}

Diameter-TEAM FORMATION problemT={algorithms,java,graphics,PH

P}{graphics,PHP,java

}{algorithms,graphi

cs}

{algorithms,graphics,java}

{PHP}

αrare= algorithmsSrare={B, E}

{PHP,java}

A B

C

E

D

E

Skills: algorithmsgraphicsjavaPHP

Diameter = 1

C

Running time: Quadratic to the number of nodes

MST – TEAM FORMATION problem•The CoverSteiner Algorithm

▫2 steps

▫First step (GreedyCover)… The social network is ignored and the

algorithm focuses on finding a set of individuals X0

▫Second step (SteinerTree)… Find the minimum cost tree that spans all the

nodes in X0

MST – TEAM FORMATION problem•SteinerTree problem

▫Required Vertices▫Steiner Vertices

▫Graph G(X,E)▫Set of Required Vertices R

▫Find G’ sub-graph of G such that G’ contains all the required vertices (R) and MST(G’) is minimized

MST – TEAM FORMATION problem•The EnhancedSteiner Algorithm

▫EnhanceGraph

A B

C

E

D

T={algorithms,java,graphics,PHP}

{graphics,PHP,java}

{algorithms,graphics}

{algorithms,graphics,java}

{PHP,java} {PHP}

PHP

java

graphics

algorithmsE

D

MST Cost = 1

Experiments•Dataset

▫DBLP dataset Database, Data Mining, Artificial Intelligence

and Theory ~6000 authors ~ 2000 distinct skills Social Network: Co-Authorship Graph

Communication Cost

Cardinality of Teams

Connectivity of the Team

Conclusion•Forming a team of skilled

▫Minimizing the communication cost

•Formulations:▫Diameter-TF problem

RarestFirst Algorithm▫MST-TF problem

CoverSteiner Algorithm EnhancedSteiner Algorithm

•Qualitative Evaluation