what-when-how
In Depth Tutorials and Information
Equation 11.13. It seems that the node
i
is connected with node
j
by a spring with
natural length
d
ij
. he potential energy resulting from the elongation of the spring
represents the error. Base on Hooke's law (
F=-kx
) the distributed algorithm can
be used to adjust the spring to minimize the total elongation of the whole system
of springs. hus, Hooke's law in the virtual coordinate system in the gravity-based
trust model is shown as below:
)
(11.14)
= −
−
−
F
k y
((
y
)
d
ij
i
j
ij
When the computation process of the virtual computation converges, each node
i
will be mapped to a coordinate value
y
i
And the trust social neighborhood relies on
the coordinate values. During the computation process new trust neighbors will be
found. he algorithm is illustrated in Figure 11.4.
f
ij
is the force between node
i
and node
j
. he
k
is spring constant;
k
t
and
k
c
represent the different characteristics
of the spring under tension and compression.
Step2.
Computingtrustlow
he trust model proposed in [18] also takes the node age parameters into account.
hus the gravity-based trust model is shown below:
For each node Xi, do:
y
i
virtual coordinate of node Xi
For each node Xi, do:
y
j
virtual coordinate of node Xj
d
ij
observed trust value between Xi and Xj
f
ij
= ((y
i
- y
j
) - d
ij
)
if ||y
i
- y
j
||> ||d
ij
||then
k = k
t
else
k = k
c
end if
y
i
= y
i
+ ukf
ij
/* u is the time step * /
End For
End For
Errvar = error variation over last
m
iterations
If errvar < €reshold, go to beginning
Figure 11.4
Pseudo code for centralized trust computation using coordinates.
(FromMaheswaran,M.,HonCheongTang,andGhunaim,A.Towardsagravity-
basedtrustmodelforsocialnetworkingsystems.
Distributed computing systems
workshops
, 2007.
27th International Conference on ICDCSW '07
. June 22-29,
2007,pp.24-24.)
