what-when-how
In Depth Tutorials and Information
11.4.7 Direct Reciprocation-Based Trust Model [23]
he importance and motivation of trust models is that they can promote the coop-
eration and reciprocity in the communities where selfish or defective behaviors are
limited by some punishment and incentive mechanisms. However, the reciprocity-
based technique requires the system to remember the previous interactions among
all nodes, which may be impossible [22]. hus, in Reference 23 it proposes a trust
model that considers the direct reciprocation. Direct reciprocity is defined as the
direct transactions between two nodes, and indirect reciprocity is defined as the
interaction with the involvement of other nodes [22,23,24], as well as the indi-
viduals adjusting their behaviors by the direct experience, which leads to limited
misreporting of information. So there are no external control mechanisms or any
form of reputation in the trust model in Reference 23.
his trust model proposed in Reference 23 is applied to the Prisoner's Dilemma,
which is a classical social dilemma where two players have to collaborate with each
other, or suppress its opponent for its own maximum proits. he payof matrix is
shown in Table 11.4 [23]. In this model the Prisoner's Dilemma plays iteratively and
at least one previous game is recorded.
In this model, also, relationships are formed based on the principle that every
node seeks to interact with another that is at least as cooperative as itself [23]. he
indicator of the cooperation is the payoff from the previous transaction. Each node
can determine whether to invite other players or accept the invitation from other
players according to the cooperation threshold [23]:
≥
⎩
v
inuite
node i will invite node
j to play the game
i
tp m
/
=
(11.17)
i j
,
<
v
node i will
not invite node j to play the game
inuite
i
Table 11.4
PayoffsforDifferentCombinationofPlayer
Strategy
Player B
Player A
Cooperate
Defect
Cooperate
1,1
−1,2
Defect
2,−1
0,0
Source:
Colombo, G. et al. Cooperation in social networks
of trust.
Self-Adaptive and Self-Organizing Systems
Workshops
, 2008.
Second IEEE International
Conference on SASOW 2008
. October 20-24, 2008,
pp. 78-83.