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| Content Provider | ACM Digital Library |
|---|---|
| Author | Gamper, Johann Timko, Igor Böhlen, Michael H. |
| Abstract | Many applications of spatio-temporal databases require support for sequenced spatio-temporal (SST) aggregation, e. g., when analyzing traffic density in a city. Conceptually, an SST aggregation produces one aggregate value for each point in time and space. This paper is the first to propose a method to efficiently evaluate SST aggregation queries for the COUNT, SUM, and AVG aggregation functions. Based on a discrete time model and a discrete, 1.5 dimensional space model that represents a road network, we generalize the concept of (temporal) constant intervals towards constant rectangles that represent maximal rectangles in the space-time domain over which the aggregation result is constant. We propose a new data structure, termed SST-tree, which extends the Balanced Tree for one-dimensional temporal aggregation towards the support for two-dimensional, spatio-temporal aggregation. The main feature of the Balanced Tree to store constant intervals in a compact way by using two counters is extended towards a compact representation of constant rectangles in the space-time domain. We propose and evaluate two variants of the SST-tree. The $SST^{T}-tree$ and $SST^{H}-tree$ use trees and hashmaps to manage spacestamps, respectively. Our experiments show that both solutions outperform a brute force approach in terms of memory and time. The $SST^{H}-tree$ is more efficient in terms of memory, whereas the $SST^{T}-tree$ is more efficient in terms of time. |
| Starting Page | 48 |
| Ending Page | 59 |
| Page Count | 12 |
| File Format | |
| ISBN | 9781605584225 |
| DOI | 10.1145/1516360.1516368 |
| Language | English |
| Publisher | Association for Computing Machinery (ACM) |
| Publisher Date | 2009-03-24 |
| Publisher Place | New York |
| Access Restriction | Subscribed |
| Content Type | Text |
| Resource Type | Article |
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