Database Reference
In-Depth Information
In the following sections, we refer in more detail to the various spatial
elements of the MultiDim model.
11.2.1 Spatial Hierarchies
All the types of hierarchies we have discussed in Sect.
4.2
apply also to spatial
hierarchies. We give next some examples of them.
Store
County
State
StoreId
StoreName
StoreAddress
...
CountyName
CountyPopulation
CountyArea
...
StateName
StatePopulation
StateArea
...
Fig. 11.7
A balanced spatial hierarchy
Figure
11.7
shows an example of a
balanced spatial hierarchy
.Note
that different spatial data types are associated with the levels of the hierarchy:
point for
Store
, surface for
County
,andsurfacesetfor
State
.Further,a
Covers
topological constraint holds in the parent-child relationships forming
the hierarchy.
District
City
Road
Segment
Number
SpeedLimit
Condition
...
DistrictName
Responsible
...
CityName
CityPopulation
...
State
StateName
StatePopulation
...
Company
CompanyName
Address
...
Fig. 11.8
A generalized spatial hierarchy
The example in Fig.
11.8
shows a
generalized spatial hierarchy
containing multiple exclusive paths that share some levels. In the example,
a road segment is related either to a district or to a company in charge of
its maintenance. The special case of
ragged hierarchies
is shown in the
Geography
hierarchy in the GeoNorthwind data warehouse (Fig.
11.4
). In the
example, a city is related either to a state or to a country. Similarly, a state
is related either to a region or to a country.
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