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5.3.2
Out-Degree Distribution
Figure 21 depicts the effect of modifying the distribution of the out-degrees of the
nodes on the average response time per object. The distribution of the out-degrees
is shown in terms of a distribution vector composed of four entries. Each entry cor-
responds to the relative number of nodes with a certain out-degree. For example, a
vector [1 : 3 : 1 : 1] represents the fact that within a DAG, 15% of nodes have no
out-degrees, 45% have out-degrees of 1, 15% have out-degree of 2, and 15% have
out-degree of 3. In general, the CCP method outperformed the LOF method. As can
be seen, when the out-degree distribution is biased to include nodes with larger out-
degrees (i.e., making the DAG denser), the LOF performance degrades at a much
faster rate than the CCP method. This is due to the fact that such bias introduces
more critical nodes and a larger number of children per node. The CCP method is
implicitly capable of handling such cases.
5 . 4
S e c t i o n C o n c l u s i o n
In the pursuit of “timely access” to public information, this section concentrated
on the proper mapping of database objects on multiple parallel air channels. The
goal was to find the most appropriate allocation scheme that would (i) preserve the
connectivity among the objects, (ii) provide the minimum overall broadcast time
F IG . 21. Average response time vs. out-degree distribution.
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