Trajectory Data Warehouses - Data Warehouse Systems: Design and Implementation - page 481

Fig. 12.6 Conceptual schema of the Northwind trajectory data warehouse
end location. Since we need to keep track of all segments belonging to a
single delivery, we define an additional dimension Delivery that groups the
data belonging to each trajectory as a whole.
As shown in the figure, there is a fact, Segment , which is related to five
dimensions: Truck , Time , Road , Delivery ,and Location . The fact is related
to the Location dimension through two roles: StartLocation and EndLocation .
Dimensions are composed of levels and hierarchies. For example, the Road
dimension has only one level, and the Location dimension is composed of
five levels, with a one-to-many parent-child relationship defined between
each couple of levels. Levels have attributes that describe their instances
or members. For example, level Road has attributes RoadId , RoadName ,and
Length . If a level or an attribute is spatial, it has an associated geometry
(e.g., point, line, or region) which is indicated by a pictogram, as studied
in the previous chapter. In our example, dimensions Road and Location are