Spatial Data Warehouses - Data Warehouse Systems: Design and Implementation - page 420

Fig. 11.1 Spatial data types
contains all the others, and the latter represent holes in the surface defined
by the former line. In simpler words, a surface may have holes but no islands
(no exterior islands and no islands within a hole).
SimpleSurface represents surfaces without holes. For example, the extent
of a lake may be represented by a surface or a simple surface, depending on
whether the lake has islands or not.
SimpleGeo is a generic spatial data type that generalizes the types
Point , Line ,and Surface . SimpleGeo is an abstract type, that is, it is never
instantiated as such: Upon creation of a SimpleGeo value, it is necessary
to specify which of its subtypes characterizes the new element. A SimpleGeo
value can be used, for instance, to generically represent cities, whereas a small
city may be represented by a point and a bigger city by a simple surface.
Several spatial data types are used to describe spatially homogeneous sets.
PointSet represents sets of points, for instance, tourist points of interest.
LineSet represents sets of lines, for example, a road network. OrientedLineSet
(a specialization of LineSet ) represents a set of oriented lines, for example,
a river and its tributaries. SurfaceSet and SimpleSurfaceSet represent sets
of surfaces with or without holes, respectively, for example, administrative
regions.
ComplexGeo represents any heterogeneous set of geometries that may
include sets of points, sets of lines, and sets of surfaces. ComplexGeo may
be used to represent a water system consisting of rivers (oriented lines),
lakes (surfaces), and reservoirs (points). ComplexGeo has PointSet , LineSet ,
OrientedLineSet , SurfaceSet ,and SimpleSurfaceSet as subtypes.
Finally, Geo is the most generic spatial data type, generalizing the types
SimpleGeo and ComplexGeo ; its semantics is “this element has a spatial