Finding a team of Experts in Social Networks

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Finding a team of Experts in Social Networks
Theodoros Lappas UC Riverside

• Joint work with Evimaria Terzi (IBM Almaden),
  Kun Liu (IBM Almaden)

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

• Given a task and a set of experts organized in a
  network, find a subset of experts that can
  effectively perform the task
• Task set of required skills
• Expert an individual with a specific skill-set
• Network represents strength of relationships

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Expertise networks

• Collaboration networks (e.g., DBLP graph,
  coauthor networks)
• Organizational structure of companies
• LinkedIn
• Geographical (map) of experts

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What makes a team effective for a task?

• T algorithms, java, graphics, python

Coverage every required skill in T is included
in the skill-set of at
least one team member
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Is coverage enough?
Talgorithms,java,graphics,python
A,E could perform the task if they could
communicate
A
D
A
A,B,C form an effective group that can communicate
B
C
E
E
C
B
Communication the members of the team must be
able to efficiently communicate and work
together
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Problem definition

• Given a task and a social network of individuals
  G, find the subset (team) of G that can
  effectively perform the given task.
• Thesis Good teams are teams that have the
  necessary skills and can also communicate
  effectively

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How to measure effective communication?
The longest shortest path between any two nodes
in the subgraph

• Diameter of the subgraph defined by the group
  members

A
D
A
B
C
E
E
C
B
diameter infty
diameter 1
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How to measure effective communication?
The total weight of the edges of a tree that
spans all the team nodes

• MST (Minimum spanning tree) of the subgraph
  defined by the group members

A
D
A
B
C
E
E
C
B
MST infty
MST 2
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Problem definition v.1.1

• Given a task and a social network G of
  individuals, find the subset (team) of
  individuals that can perform the given task and
  define a subgraph in G with the minimum diameter.
• Problem is NP-hard

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The RarestFirst algorithm
Talgorithms,java,graphics,python
graphics,python,java
algorithms,graphics
B
A
A
B
Skills algorithms graphics java python
E
E
algorithms,graphics,java
C
D
python,java
python
arare algorithms SrareBob, Eleanor
Diameter 2
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The RarestFirst algorithm
Talgorithms,java,graphics,python
graphics,python,java
algorithms,graphics
A
B
Skills algorithms graphics java python
E
E
algorithms,graphics,java
C
C
D
python,java
python
arare algorithms SrareBob, Eleanor
Diameter 1
Running time Quadratic to the number of
nodes Approximation factor 2xOPT
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Problem definition v.1.2

• Given a task and a social network G of
  individuals, find the subset (team) of
  individuals that can perform the given task and
  define a subgraph in G with the minimum MST cost.
• Problem is NP-hard

Best known Approximation factor O(log3n log k)
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The SteinerTree problem

• Graph G(V,E)
• Set of Required Vertices R
• Find G subgraph of G such that G contains all
  the required vertices (R) and MST(G) is minimized

Required vertices
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The EnhancedSteiner algorithm
Talgorithms,java,graphics,python
graphics
graphics,python,java
algorithms,graphics
A
B
java
algorithms
E
E
algorithms,graphics,java
D
C
D
python
python,java
python
MST Cost 1
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Experiments
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Dataset
DBLP Dataset ( DM, AI, DB, T ) 6000
authors Skills keywords appearing in paper
titles 2000 features Social Network
Co-Authorship Graph Tasks Subsets of keywords
with different cardinality
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Cardinality of teams
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Example teams (I)

• S. Brin, L. Page The anatomy of a large-scale
  hypertextual Web search engine
• Paolo Ferragina, Patrick Valduriez, H. V.
  Jagadish, Alon Y. Levy, Daniela Florescu, Divesh
  Srivastava, S. Muthukrishnan
• P. Ferragina ,J. Han, H. V.Jagadish, Kevin
  Chen-Chuan Chang, A. Gulli, S. Muthukrishnan,
  Laks V. S. Lakshmanan

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Example teams (II)

• J. Han, J. Pei, Y. Yin Mining frequent patterns
  without candidate generation
• F. Bonchi
• A. Gionis, H. Mannila, R. Motwani

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Extensions

• Other measures of effective communication
• Other practical restrictions
• Incorporate ability levels

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• Thanks for your attention!