Trajectory Data Warehouses - Data Warehouse Systems: Design and Implementation - page 471

20 30

Salary
John

60

Salary
Mary

20 40 60 45 60

Avg

2012-01-01 2012-04-01 2012-07-01 2012-10-01 2013-01-01 2013-04-01

Fig. 12.2 Graphical representation of the temporal average

12.2.1 Temporal Spatial Types

All operations for temporal types discussed so far are also valid for spatial
types. For example, a value of type temporal(point) , which can represent the
trajectory of a truck, is a continuous function f : instant point .

We will present now some of the specific operations of Table 12.1 for
thespatialcase.Wewilluseasexampletwotemporalpoints RouteT1 and
RouteT2 , which keep track of the delivery routes followed by two trucks T1
and T2 on the same day, say, January 10, 2012. A graphical representation
of the trajectories of the two trucks is given in Fig. 12.3 . We can see, for
instance, that truck T1 took 10min to go from point (0,0) to point (2,2),
and then it stopped for 15min at that point. In this example, we assume a
cons ta nt speed between pairs of points. Thus, truck T1 traveled a distance

→

of √ 8=2 . 83 in 10min, while truck T2 traveled a distance of √ 5=2 . 23 in
the first 10min and a distance of 1 in the following 5min.

Y 8:25

8:10

8:20

2

T1

8:15

1

T2

8:00

1 2 3 X

8:05

Fig. 12.3 Graphical representation of the trajectories of two trucks

The operation Trajectory projects temporal geometries into the plane (see
Table 12.1 ). The projection of a temporal point into the plane may consist of
points and lines, while the projection of a temporal line into the plane may