the costs on experts and interactions were weighted and
summed as input values of edges in a social network, and the
heuristic algorithm was adopted to update and evolve team
schemes iteratively until the termination conditions for the best
scheme were satisfied (Kargar et al. 2012, 2013a, b). However,
their model did not cope with the issue of unifying the
cost-related quantities since they depend on the scope of
anticipated properties of team candidates. In addition, they
failed to give two cost utility functions. Reexamining the
example in Fig. 1, the sum of expert cost of team A is 70 Yuan;
while the interaction cost of the team is 0.1. The summation of
expert cost and interaction cost became pointless if the
unification or normalization of quantities were not performed.
The team formation problem will become very challenging
when the pool of expert candidates is large in a social network, it
takes intensive computation in evaluating a large number of
team candidates to update and evolve better team schemes.
To solve the aforementioned problems in existing team
formation models, we propose a new method called the
Skyline-based Team Formation (SkylineTF), where the notion
of Skyline is adopted in the team formation model. Firstly, a
social network is analyzed by the method of betweenness
centrality to select seeds of experts, and the utility functions are
used to convert expert quality vectors into real values. Secondly,
the notions of Skyline are adopted to obtain expert candidates
that are not dominated by other experts. Thirdly, the weights of
cost aggregate functions are adjusted iteratively until the expert
team is formed according to the termination condition of
optimization. Finally, we conduct the experiment to illustrate
the effectiveness of the proposed method in comparison with
existing models in sense that the searching time for expert
candidates has been reduced remarkably.
The rest of the paper is organized as follows. In Section II, we
discuss the relevant work on the methodologies for team
formation. In Section III, the concept of the team discovery
model is defined and discussed. In Section IV, a new team
discovery model is proposed for crowdsourcing tasks. In
Section V, the new algorithm is developed to assign tasks to an
expert team in a social network automatically. In Section VI, the
experiment is reported as the validation of the proposed method.
Finally, a summary of the presented work is provided with a
brief discussion of future work in Section VII.
II. R
ELATED
W
ORKS
In this work, we focus on the discovery of an expert team in a
social network to accomplish a specified project. The success of
the project is measured by the effectiveness and engagement
levels of team members in collaboration and communication. In
other words, the primary objective of the team formation is to
minimize the operation cost of the developed team in fulfilling
the specified business missions. Therefore, it is crucial to take
into account of the effectiveness of collaborations in identifying
team members. The pioneer work in developing an expert team
from a social network was made Lappas et al. (2009); they
implemented two algorithms form expert teams based on an
analysis of existing relations. Li et al. (2013) generalized the
team formation problem in sense that every required skill is
associated with a given number of experts; their goal was to
improve the effectiveness and efficiency of the developed team.
Anagnostopoulos et al. (2012) also discussed the factor of the
balance of experts’ workload, and took into account in the team
formation. In the method proposed by Majumder et al. (2012),
the criterion that no expert member took an overload was placed
as a constraint in identifying team members. In the
aforementioned algorithms (Lappas et al. 2009,
Anagnostopoulos et al. 2010, Anagnostopoulos et al. 2012,
Datta et al. 2012, Li et al. 2013), the effectiveness of
collaboration was represented by either of two cost functions,
i.e., diameter communication cost and minimum spanning tree
cost.
The roles of participators in a team are not necessary the
same. For some projects, the project team requires to specify a
team leader who is in charge of overseeing the activities and
coordinating team members for the project (Kargar and An
2011). In such scenarios, each team member needs to
communicate with the project leader directly to update the
progresses of the ongoing activities; the team leader is
responsible of performing its decision-making activities to
guide the members for effective collaboration at the project
level. However, neither of the diameter communication cost or
minimum spanning tree cost is appropriate under such
circumstances.
To solve this problem, Kargar and An (2011) defined a
project leader who was in charge of coordinating activities in
their team formation. New cost function type called the leader
cost function is defined to measure the cost of the
communication of the leader with associated members. In
optimizing the selection of the leader and associated team
members, Kargar et al. (2013a, b) used the brute-force
algorithm to evaluate each potential member as a candidate
leader and identify its team member with the leader. Therefore,
the best team was defined by evaluating and comparing all the
candidates in the social network exhaustively; the brute-force
algorithm required intensive computations when the number of
qualified experts in the network is large. To reduce computation
in team formation, Juang et al. (2013) selected a member with
multiple shortest paths as the leader candidate for a lower
collaboration cost. Since the communication cost was measured
by the geographic distances of the leader and team members, the
concept of the betweenness centrality was used as the selection
criterion for a project leader. Their experiments illustrated the
improved algorithm generated better outcomes.
All of the above algorithms were developed to form project
teams from social networks. However, the common drawbacks
of these algorithms were the lack of considerations on labor
costs of experts. In the real-world business, most of expert
services are available by pay for services, and service rates vary
from one expert to another even for the same nature of
responsibility in project. Therefore, the cost evaluation merely
on team interactions is insufficient. It is desirable that the expert
team discovery model take into consideration of both of labor
cost and interaction cost of the team. Some preliminary works
by Kargar et al. (2012, 2013a, b) took a weighted summation of
labor cost and interaction cost as the attributes of edges in the
graphic representation of team in a social network; they
suggested to use a heuristic algorithm to optimize the team
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