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Fig. 8.20
Example of the
signal propagation process
within a peer; (
a
)forward
propagation: the signal from
the query templates
g
1
and
g
4
in the second layer is sent to
the third layer (video nodes);
(
b
) backward propagation:
the signal from the activated
video nodes,
v
1
,
v
3
and
v
4
is
sent back to the second layer.
As a result, the templates
g
1
,
g
3
,and
g
6
are newly
discovered and set as the
relevant template nodes
w
ij
∑
w
ij
=
(8.20)
J
j
=
1
w
ij
where
a
(
v
)
i
is the activation level of the
i
-th video node and
Pos
is the set of
i
's such
that
a
(
v
)
i
>
Tr
, where
Tr
is a threshold value.
8.5.3.2
Inter-Peer Signal Propagation
As shown by the example in Fig.
8.20
, the forward-backward signal propagation
process will introduce new template nodes which are relevant to the query. We draw
on the observation that, with more templates in the query, it is more likely that a
video relevant to this query is indexed under at least one of the query templates. This
process automatically expands a short query with additional relevant templates. The
activation level
a
(
g
)
j
in Eq. (
8.19
) can be viewed as the degree of relevance of the
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