(mysql.info.gz) GIS geometry class hierarchy
Info Catalog
(mysql.info.gz) OpenGIS geometry model
(mysql.info.gz) OpenGIS geometry model
(mysql.info.gz) GIS class geometry
18.2.1 The Geometry Class Hierarchy
-----------------------------------
The geometry classes define a hierarchy as follows:
* `Geometry' (non-instantiable)
* `Point' (instantiable)
* `Curve' (non-instantiable)
* `LineString' (instantiable)
* `Line'
* `LinearRing'
* `Surface' (non-instantiable)
* `Polygon' (instantiable)
* `GeometryCollection' (instantiable)
* `MultiPoint' (instantiable)
* `MultiCurve' (non-instantiable)
* `MultiLineString' (instantiable)
* `MultiSurface' (non-instantiable)
* `MultiPolygon' (instantiable)
It is not possible to create objects in non-instantiable classes. It
is possible to create objects in instantiable classes. All classes
have properties, and instantiable classes may also have assertions
(rules that define valid class instances).
`Geometry' is the base class. It's an abstract class. The instantiable
subclasses of `Geometry' are restricted to zero-, one-, and
two-dimensional geometric objects that exist in two-dimensional
coordinate space. All instantiable geometry classes are defined so that
valid instances of a geometry class are topologically closed (that is,
all defined geometries include their boundary).
The base `Geometry' class has subclasses for `Point', `Curve',
`Surface', and `GeometryCollection':
* `Point' represents zero-dimensional objects.
* `Curve' represents one-dimensional objects, and has subclass
`LineString', with sub-subclasses `Line' and `LinearRing'.
* `Surface' is designed for two-dimensional objects and has subclass
`Polygon'.
* `GeometryCollection' has specialized zero-, one-, and
two-dimensional collection classes named `MultiPoint',
`MultiLineString', and `MultiPolygon' for modeling geometries
corresponding to collections of `Points', `LineStrings', and
`Polygons', respectively. `MultiCurve' and `MultiSurface' are
introduced as abstract superclasses that generalize the collection
interfaces to handle `Curves' and `Surfaces'.
`Geometry', `Curve', `Surface', `MultiCurve', and `MultiSurface' are
defined as non-instantiable classes. They define a common set of
methods for their subclasses and are included for extensibility.
`Point', `LineString', `Polygon', `GeometryCollection', `MultiPoint',
`MultiLineString', and `MultiPolygon' are instantiable classes.
Info Catalog
(mysql.info.gz) OpenGIS geometry model
(mysql.info.gz) OpenGIS geometry model
(mysql.info.gz) GIS class geometry
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