'Generating and Indexing Multi-Dimensional Moving Regions in Spatio-Temporal Databases'
Studenteropgave: Kandidatspeciale og HD afgangsprojekt
- Jens Frøkjær
- Palle B. Hansen
- Ivan V. S. Larsen
- Tom Oddershede
4. semester, Datalogi, Kandidat (Kandidatuddannelse)
'The number of modifications is typically orders of magnitude higher
than the number of queries on a database that stores moving regions.
However, the predominant index structure for moving regions is the
R+-tree and this structure handles spatial queries better than
modifications. To address this problem a new indexing technique,
called Layered Shifted Space-filling curves (LSS), is presented. LSS
is optimized for modifications. It uses shifted layers in order to
assign only a single index value to each region. Shifting layers
guarantees that moving regions of a certain size always fit on a
particular layer. A problem with canonical use of space-filling
curves is that it requires prior knowledge of the data to be
indexed. A self maintenance method for the LSS technique is proposed
which makes LSS work without a prior knowledge of the data, e.g,
world size. A performance study using the Oracle DBMS compares LSS
to Oracle’s R+-trees and existing space-filling curve approaches.
This study shows that LSS, compared to Oracle’s R+-trees, is up
to 35 times faster for modifications at the expense of being up to
11 times slower for queries. Synthetic data is often preferred for
performance testing as it is easy to control the conditions. This
paper also proposes both a data and workload generator for
generating n-dimensional moving objects. The data generator uses
statistical distributions for moving and resizing the objects. When
testing an index it is often desired to test a mix of modifications
and queries. Therefore, this paper also provides a workload
generator which produces a mix of inserts, updates, deletes, and
spatial queries. A performance study shows that STDW is able to
produce 27,000 object snapshots per second on a standard PC.
'
Sprog | Engelsk |
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Udgivelsesdato | jun. 2006 |