1. Presentation : Finding a Team of Experts in Social Networks Jack Cheng Ka Ho The Chinese University of Hong Kong SEEM 5010 Advanced Database and Information System

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

3. 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

4. Expertise Networks Companies (Organizational Structure): ▫Same group or department  Easily Communicate Research Community: ▫Collaboration Networks Other examples of Social Networks ▫LinkedIn, Xing and others

5. 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 {algorithms} B {web programming} B D {software engineering} C {software engineering, distributed systems} E {software engineering, distributed systems, web programming} A {algorithms} B {web programming} B C {software engineering, distributed systems} E {software engineering, distributed systems, web programming} A {algorithms}

6. 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 engineering} B {web programming} B C {software engineering, distributed systems} E {software engineering, distributed systems, web programming} A {algorithms} AA BBCC DD EE A, B and C form an effective group to communicate A and E could perform task if they could communicate

7. 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

8. 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 BCE DA ECB diameter = infty diameter = 1

9. 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 BCE DA ECB MST = infty MST = 2

10. Diameter-TEAM FORMATION problem AB C E D T={ algorithms,java,graphics,PHP } {graphics,PHP,java} {algorithms,graphics} {algorithms,graphics,java} {PHP} α rare = algorithms S rare ={B, E} α rare = algorithms S rare ={B, E} B E A Skills: algorithms graphics java PHP Diameter = 2 α rare = java S rare ={A, C, E} α rare = java S rare ={A, C, E} α rare = PHP S rare ={A,C,D} α rare = PHP S rare ={A,C,D} {PHP,java}

11. Diameter-TEAM FORMATION problem T={ algorithms,java,graphics,PHP } {graphics,PHP,java} {algorithms,graphics} {algorithms,graphics,java} {PHP} α rare = algorithms S rare ={B, E} α rare = algorithms S rare ={B, E} {PHP,java} AB C E D E Skills: algorithms graphics java PHP Diameter = 1 C Running time: Quadratic to the number of nodes

12. 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 X 0 ▫Second step (SteinerTree)…  Find the minimum cost tree that spans all the nodes in X 0

13. 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

14. MST – TEAM FORMATION problem The EnhancedSteiner Algorithm ▫EnhanceGraph AB C E D T={ algorithms,java,graphics,PHP } {graphics,PHP,java} {algorithms,graphics} {algorithms,graphics,java} {PHP,java}{PHP} PHP java graphics algorithms E D MST Cost = 1

15. Experiments Dataset ▫DBLP dataset  Database, Data Mining, Artificial Intelligence and Theory  ~6000 authors  ~ 2000 distinct skills  Social Network: Co-Authorship Graph

16. Communication Cost

17. Cardinality of Teams

18. Connectivity of the Team

19. 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