what-when-how
In Depth Tutorials and Information
−
T T d
i
s
(
r
)
ij
n
ij
(11.15)
=
λ
Trust
ij
r
3
ij
where
T
ij
is the age of node
j
as estimated by node
i
, and
T
i
s
is the age of the system
as estimated by node
i
.
r
ij
is the distance calculated from the virtual coordinate
r
ij
=
y
i
-y
j
.
he simulation results of the gravity-based trust model [18] show that trust
estimation error varies with number of nodes, and the spring has no additional
stifness. his means a spring constant equal to 1 is the best scenario.
(a) (b)
However, due to the shortcomings of the small world theory, only the short-
est tie between source and target is considered, and some useful information is
ignored by eliminating some ties in trust computation. hus, we will introduce a
new model based on electric circuit theory to solve the problem.
In Reference 17, an interesting trust model is proposed called RN-trust where
an STN is mapped to a resistive network. A resistive network consists of resistors
that are connected in series and parallel. It can reflect some properties of STNs such
as transitivity and asymmetry. Every node in the STNs is replaced by a node in the
resistive network. A resistor is placed between the nodes that have a trust relation-
ship (see Figure 11.5). An ideal diode is used to realize the asymmetry property of
sociotechnical network. hus, the resistors' values must have a reverse relation with
the trust values [17].
= −
log
resistance
trust
(11.16)
By the methods of circuit analysis the equivalent resistance of the electric circuit
can be used as a measure to calculate the trust value from the source to the sink
after establishing the resistive network [17]. All links are taken into account in this
model so no information is ignored. Besides, the time complexity of RN-trust is
comparable to other models. However, now the RN-trust model cannot totally
simulate the sociotechnical work so it should be improved by adding more aspects
of trust through including more electronic elements to the resistive network.
u
u
u
-Log(t)
v
Ideal Diode
Figure 11.5
(a) An edge in a trust network with the trust value t from u to v;
(b)Correspondingedgeintheresistivenetwork.(FromTaherian,M.etal.Trust
inference in web-based social networks using resistive networks.
Internet and
Web Applications and Services
,
2008
.
Third International Conference on ICIW
'08
.June8-13,2008,pp.233-238.)
