Information Technology Reference
In-Depth Information
F
IG
. 22. Response time vs. number of retrieved classes.
to the increase in the total number of objects to be retrieved assuming that the ob-
jects to be retrieved are distributed uniformly along the broadcast. In addition, the
single-class method offers a better response time than the hierarchical case, and
the response time for the single-class method increases as the number of retrieved
classes increase. The first observation is because of the fact that in the single-class
method accesses do not have to be directed to the beginning of the broadcast. When
a probe takes place, the first class belonging to the set of classes to be retrieved can
be accessed directly. Other required classes are accessed in sequence. The second
observation is due to the fact that an increase in the number of classes to be retrieved
directly increases the number of index and data pages to be accessed. Finally, index-
ing based on the aggregation relationship offers lower response time than indexing
based on the inheritance relationship, since the distribution of the number of objects
in the inheritance relationship is more concentrated on the larger objects. Having
larger objects results in a longer broadcast, and hence, longer time to retrieve the
objects.
6.1.3.2 Energy Consumption.
For each query, the amount of energy
consumed is the sum of the consumed energy while the unit is in both active and
doze modes. In the case where no index is provided, the mobile unit is in active
mode during the entire probe. However, in the case where an index is provided, the
active time is proportional to the number of index and data pages to be retrieved. As
expected, the active time of each case increases as the number of retrieved classes
