Trajectory Data Warehouses - Data Warehouse Systems: Design and Implementation - page 483

Fig. 12.7 An alternative segmentation of trajectories with respect to delivery zones
The data warehouse of Fig. 12.6 segments trajectories with respect to
days, roads, trucks, start locations, and end locations. An alternative schema,
shown in Fig. 12.7 , segments trajectories with respect to the delivery zones in
which they occur. Notice that, as stated by the many-to-many relationship
between zones and cities, a delivery zone can span several cities, and a city
can be split in several delivery zones. Notice also that the time granularity
in Figs. 12.6 and 12.7 differs. In the former case, the granularity is day,
although we keep the movement track in the Route measure with a timestamp
granularity. In the latter case, we relate each segment with its initial and final
timestamps. The choice among the two alternative data warehouse schemas
depends on application requirements and the typical OLAP queries to be
addressed.
When trajectories are used as measures, the problem of aggregation
arises. In the examples of Figs. 12.6 and 12.7 , we kept the movement track