Information Technology Reference
In-Depth Information
F
IG
. 23. Active time vs. number of the retrieved classes.
increases (
Fig. 23
). In general, the hierarchical method requires less active time than
the single-class method. The hierarchical method searches only one large index tree,
whereas the single-class method searches through multiple smaller index trees. The
number of pages retrieved per index tree is proportional to the height of the tree.
For a query spanning a single class, the single-class method produces a better ac-
tive time than the hierarchical method. As the number of classes to be retrieved
increases, the hierarchical tree is still traversed only once. However, more single-
class trees have to be traversed, and hence, resulting in an increase in the active
time.
In both the single-class and the hierarchical methods, the aggregation case requires
lower active time than the inheritance case. This is simply due to the fact that the
inheritance case has larger objects and thus, requires the retrieval of more pages.
6 . 2
I n d e x i n g o n P a r a l l e l A i r C h a n n e l s
Retrieval of data from an air channel at the mobile host (MH) is somewhat limited
by the MH's power supply. In an effort to reduce power consumption and response
time, this section investigates the application of indexing, the organization, and the
distribution of objects along the parallel air channels
[9]
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