Finding a Team of ExpertsFinding a Team of Expertsin Social Networksin Social Networks

SEEM 5010 Advanced Database and Information SystemSEEM 5010 Advanced Database and Information System

Theodoros Lappas (UC Riverside)Evimaria Terzi (IBM Almaden)Kun Liu (IBM Almaden)

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 How can I find a team of experts a team of experts that can that can collaborate effectively collaborate effectively in in order to complete a given task?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}

AA{{algorithmalgorithm

ss}}

BB{{web web

programminprogrammingg}}

DD{{software software engineerinengineerin

gg}}

CC{{software software

engineeringengineering, , distributed distributed systemssystems}}

EE{{software software

engineeringengineering, , distributed systemsdistributed systems, , web programmingweb programming}}

AA{{algorithmalgorithm

ss}}

BB{{web web

programminprogrammingg}}

CC{{software software

engineeringengineering, , distributed distributed systemssystems}}

EE{{software software

engineeringengineering, , distributed systemsdistributed systems, , web programmingweb programming}}

AA{{algorithmalgorithm

ss}}

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}

DD{{software software engineerinengineerin

gg}}

BB{{web web

programminprogrammingg}}

CC{{software software

engineeringengineering, , distributed distributed systemssystems}}

EE{{software software

engineeringengineering, , distributed systemsdistributed systems, , web programmingweb programming}}

AA{{algorithmalgorithm

ss}}

AA

BB CC

DD

EE

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 X’ have the necessary necessary

skillsskills

EE= = EdgeEdge

How to measure effective communication?The author proposed two measures:

•Diameter•Minimum Spanning Tree

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 = inftydiameter = 1diameter = 1

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 = inftyMST = 2MST = 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 problem

T={algorithms,java,graphics,PHP}

{graphics,PHP,java}

{algorithms,graphics}

{algorithms,graphics,java}

{PHP}

αrare= algorithmsSrare={B, E}

{PHP,java}

A B

C

E

D

E

Skills: algorithmsgraphicsjavaPHP

Diameter = 1

C

Running time: Running time: Quadratic Quadratic to the number of nodesto 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 Choose about 6000 authors

Skills: Define keywords appearing in paper titles as skills, about 2000 distinct skills

Social Network: Co-Authorship Graph Tasks: Subsets of keywords with different

cardinality

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